7 files changed, 68 insertions, 15 deletions
diff --git a/AndroidKernel.mk b/AndroidKernel.mk
index 3db9ac9f0bcb..beefecad0ab0 100644
--- a/AndroidKernel.mk
+++ b/AndroidKernel.mk
@@ -6,6 +6,13 @@ ifeq ($(KERNEL_TARGET),)
 INSTALLED_KERNEL_TARGET := $(PRODUCT_OUT)/kernel
 endif
 
+TARGET_KERNEL_MAKE_ENV := $(strip $(TARGET_KERNEL_MAKE_ENV))
+ifeq ($(TARGET_KERNEL_MAKE_ENV),)
+KERNEL_MAKE_ENV :=
+else
+KERNEL_MAKE_ENV := $(TARGET_KERNEL_MAKE_ENV)
+endif
+
 TARGET_KERNEL_ARCH := $(strip $(TARGET_KERNEL_ARCH))
 ifeq ($(TARGET_KERNEL_ARCH),)
 KERNEL_ARCH := arm
@@ -91,8 +98,8 @@ TARGET_PREBUILT_INT_KERNEL := $(TARGET_PREBUILT_INT_KERNEL)-dtb
 endif
 
 KERNEL_HEADERS_INSTALL := $(KERNEL_OUT)/usr
-KERNEL_MODULES_INSTALL := system
-KERNEL_MODULES_OUT := $(TARGET_OUT)/lib/modules
+KERNEL_MODULES_INSTALL ?= system
+KERNEL_MODULES_OUT ?= $(PRODUCT_OUT)/$(KERNEL_MODULES_INSTALL)/lib/modules
 
 TARGET_PREBUILT_KERNEL := $(TARGET_PREBUILT_INT_KERNEL)
 
@@ -124,43 +131,43 @@ $(KERNEL_OUT):
 	mkdir -p $(KERNEL_OUT)
 
 $(KERNEL_CONFIG): $(KERNEL_OUT)
-	$(MAKE) -C $(TARGET_KERNEL_SOURCE) O=$(BUILD_ROOT_LOC)$(KERNEL_OUT) ARCH=$(KERNEL_ARCH) CROSS_COMPILE=$(KERNEL_CROSS_COMPILE) $(KERNEL_DEFCONFIG)
+	$(MAKE) -C $(TARGET_KERNEL_SOURCE) O=$(BUILD_ROOT_LOC)$(KERNEL_OUT) $(KERNEL_MAKE_ENV) ARCH=$(KERNEL_ARCH) CROSS_COMPILE=$(KERNEL_CROSS_COMPILE) $(KERNEL_DEFCONFIG)
 	$(hide) if [ ! -z "$(KERNEL_CONFIG_OVERRIDE)" ]; then \
 			echo "Overriding kernel config with '$(KERNEL_CONFIG_OVERRIDE)'"; \
 			echo $(KERNEL_CONFIG_OVERRIDE) >> $(KERNEL_OUT)/.config; \
-			$(MAKE) -C $(TARGET_KERNEL_SOURCE) O=$(BUILD_ROOT_LOC)$(KERNEL_OUT) ARCH=$(KERNEL_ARCH) CROSS_COMPILE=$(KERNEL_CROSS_COMPILE) oldconfig; fi
+			$(MAKE) -C $(TARGET_KERNEL_SOURCE) O=$(BUILD_ROOT_LOC)$(KERNEL_OUT) $(KERNEL_MAKE_ENV) ARCH=$(KERNEL_ARCH) CROSS_COMPILE=$(KERNEL_CROSS_COMPILE) oldconfig; fi
 
 $(TARGET_PREBUILT_INT_KERNEL): $(KERNEL_OUT) $(KERNEL_HEADERS_INSTALL)
 	$(hide) echo "Building kernel..."
 	$(hide) rm -rf $(KERNEL_OUT)/arch/$(KERNEL_ARCH)/boot/dts
-	$(MAKE) -C $(TARGET_KERNEL_SOURCE) O=$(BUILD_ROOT_LOC)$(KERNEL_OUT) ARCH=$(KERNEL_ARCH) CROSS_COMPILE=$(KERNEL_CROSS_COMPILE) $(KERNEL_CFLAGS)
-	$(MAKE) -C $(TARGET_KERNEL_SOURCE) O=$(BUILD_ROOT_LOC)$(KERNEL_OUT) ARCH=$(KERNEL_ARCH) CROSS_COMPILE=$(KERNEL_CROSS_COMPILE) $(KERNEL_CFLAGS) modules
-	$(MAKE) -C $(TARGET_KERNEL_SOURCE) O=$(BUILD_ROOT_LOC)$(KERNEL_OUT) INSTALL_MOD_PATH=$(BUILD_ROOT_LOC)../$(KERNEL_MODULES_INSTALL) INSTALL_MOD_STRIP=1 ARCH=$(KERNEL_ARCH) CROSS_COMPILE=$(KERNEL_CROSS_COMPILE) modules_install
+	$(MAKE) -C $(TARGET_KERNEL_SOURCE) O=$(BUILD_ROOT_LOC)$(KERNEL_OUT) $(KERNEL_MAKE_ENV) ARCH=$(KERNEL_ARCH) CROSS_COMPILE=$(KERNEL_CROSS_COMPILE) $(KERNEL_CFLAGS)
+	$(MAKE) -C $(TARGET_KERNEL_SOURCE) O=$(BUILD_ROOT_LOC)$(KERNEL_OUT) $(KERNEL_MAKE_ENV) ARCH=$(KERNEL_ARCH) CROSS_COMPILE=$(KERNEL_CROSS_COMPILE) $(KERNEL_CFLAGS) modules
+	$(MAKE) -C $(TARGET_KERNEL_SOURCE) O=$(BUILD_ROOT_LOC)$(KERNEL_OUT) INSTALL_MOD_PATH=$(BUILD_ROOT_LOC)../$(KERNEL_MODULES_INSTALL) INSTALL_MOD_STRIP=1 $(KERNEL_MAKE_ENV) ARCH=$(KERNEL_ARCH) CROSS_COMPILE=$(KERNEL_CROSS_COMPILE) modules_install
 	$(mv-modules)
 	$(clean-module-folder)
 
 $(KERNEL_HEADERS_INSTALL): $(KERNEL_OUT)
 	$(hide) if [ ! -z "$(KERNEL_HEADER_DEFCONFIG)" ]; then \
 			rm -f $(BUILD_ROOT_LOC)$(KERNEL_CONFIG); \
-			$(MAKE) -C $(TARGET_KERNEL_SOURCE) O=$(BUILD_ROOT_LOC)$(KERNEL_OUT) ARCH=$(KERNEL_HEADER_ARCH) CROSS_COMPILE=$(KERNEL_CROSS_COMPILE) $(KERNEL_HEADER_DEFCONFIG); \
-			$(MAKE) -C $(TARGET_KERNEL_SOURCE) O=$(BUILD_ROOT_LOC)$(KERNEL_OUT) ARCH=$(KERNEL_HEADER_ARCH) CROSS_COMPILE=$(KERNEL_CROSS_COMPILE) headers_install; fi
+			$(MAKE) -C $(TARGET_KERNEL_SOURCE) O=$(BUILD_ROOT_LOC)$(KERNEL_OUT) $(KERNEL_MAKE_ENV) ARCH=$(KERNEL_HEADER_ARCH) CROSS_COMPILE=$(KERNEL_CROSS_COMPILE) $(KERNEL_HEADER_DEFCONFIG); \
+			$(MAKE) -C $(TARGET_KERNEL_SOURCE) O=$(BUILD_ROOT_LOC)$(KERNEL_OUT) $(KERNEL_MAKE_ENV) ARCH=$(KERNEL_HEADER_ARCH) CROSS_COMPILE=$(KERNEL_CROSS_COMPILE) headers_install; fi
 	$(hide) if [ "$(KERNEL_HEADER_DEFCONFIG)" != "$(KERNEL_DEFCONFIG)" ]; then \
 			echo "Used a different defconfig for header generation"; \
 			rm -f $(BUILD_ROOT_LOC)$(KERNEL_CONFIG); \
-			$(MAKE) -C $(TARGET_KERNEL_SOURCE) O=$(BUILD_ROOT_LOC)$(KERNEL_OUT) ARCH=$(KERNEL_ARCH) CROSS_COMPILE=$(KERNEL_CROSS_COMPILE) $(KERNEL_DEFCONFIG); fi
+			$(MAKE) -C $(TARGET_KERNEL_SOURCE) O=$(BUILD_ROOT_LOC)$(KERNEL_OUT) $(KERNEL_MAKE_ENV) ARCH=$(KERNEL_ARCH) CROSS_COMPILE=$(KERNEL_CROSS_COMPILE) $(KERNEL_DEFCONFIG); fi
 	$(hide) if [ ! -z "$(KERNEL_CONFIG_OVERRIDE)" ]; then \
 			echo "Overriding kernel config with '$(KERNEL_CONFIG_OVERRIDE)'"; \
 			echo $(KERNEL_CONFIG_OVERRIDE) >> $(KERNEL_OUT)/.config; \
-			$(MAKE) -C $(TARGET_KERNEL_SOURCE) O=$(BUILD_ROOT_LOC)$(KERNEL_OUT) ARCH=$(KERNEL_ARCH) CROSS_COMPILE=$(KERNEL_CROSS_COMPILE) oldconfig; fi
+			$(MAKE) -C $(TARGET_KERNEL_SOURCE) O=$(BUILD_ROOT_LOC)$(KERNEL_OUT) $(KERNEL_MAKE_ENV) ARCH=$(KERNEL_ARCH) CROSS_COMPILE=$(KERNEL_CROSS_COMPILE) oldconfig; fi
 
 kerneltags: $(KERNEL_OUT) $(KERNEL_CONFIG)
-	$(MAKE) -C $(TARGET_KERNEL_SOURCE) O=$(BUILD_ROOT_LOC)$(KERNEL_OUT) ARCH=$(KERNEL_ARCH) CROSS_COMPILE=$(KERNEL_CROSS_COMPILE) tags
+	$(MAKE) -C $(TARGET_KERNEL_SOURCE) O=$(BUILD_ROOT_LOC)$(KERNEL_OUT) $(KERNEL_MAKE_ENV) ARCH=$(KERNEL_ARCH) CROSS_COMPILE=$(KERNEL_CROSS_COMPILE) tags
 
 kernelconfig: $(KERNEL_OUT) $(KERNEL_CONFIG)
 	env KCONFIG_NOTIMESTAMP=true \
-	     $(MAKE) -C $(TARGET_KERNEL_SOURCE) O=$(BUILD_ROOT_LOC)$(KERNEL_OUT) ARCH=$(KERNEL_ARCH) CROSS_COMPILE=$(KERNEL_CROSS_COMPILE) menuconfig
+	     $(MAKE) -C $(TARGET_KERNEL_SOURCE) O=$(BUILD_ROOT_LOC)$(KERNEL_OUT) $(KERNEL_MAKE_ENV) ARCH=$(KERNEL_ARCH) CROSS_COMPILE=$(KERNEL_CROSS_COMPILE) menuconfig
 	env KCONFIG_NOTIMESTAMP=true \
-	     $(MAKE) -C $(TARGET_KERNEL_SOURCE) O=$(BUILD_ROOT_LOC)$(KERNEL_OUT) ARCH=$(KERNEL_ARCH) CROSS_COMPILE=$(KERNEL_CROSS_COMPILE) savedefconfig
+	     $(MAKE) -C $(TARGET_KERNEL_SOURCE) O=$(BUILD_ROOT_LOC)$(KERNEL_OUT) $(KERNEL_MAKE_ENV) ARCH=$(KERNEL_ARCH) CROSS_COMPILE=$(KERNEL_CROSS_COMPILE) savedefconfig
 	cp $(KERNEL_OUT)/defconfig $(TARGET_KERNEL_SOURCE)/arch/$(KERNEL_ARCH)/configs/$(KERNEL_DEFCONFIG)
 
 endif
diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index cbfb3f4428e0..2d85e309477a 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -1030,6 +1030,11 @@ config BUILD_ARM64_APPENDED_DTB_IMAGE_NAMES
 	  Space separated list of names of dtbs to append when
 	  building a concatenated Image.gz-dtb.
 
+config BUILD_ARM64_DT_OVERLAY
+	bool "enable DT overlay compilation support"
+	depends on OF
+	help
+	  This option enables support for DT overlay compilation.
 endmenu
 
 menu "Userspace binary formats"
diff --git a/arch/arm64/Makefile b/arch/arm64/Makefile
index 101632379b8b..fcfa3c7dedc1 100644
--- a/arch/arm64/Makefile
+++ b/arch/arm64/Makefile
@@ -92,6 +92,10 @@ endif
 
 KBUILD_DTBS	:= dtbs
 
+ifeq ($(CONFIG_BUILD_ARM64_DT_OVERLAY),y)
+export DTC_FLAGS := -@
+endif
+
 all:	$(KBUILD_IMAGE) $(KBUILD_DTBS)
 
 boot := arch/arm64/boot
diff --git a/scripts/Makefile.build b/scripts/Makefile.build
index 01df30af4d4a..45473ca4290c 100644
--- a/scripts/Makefile.build
+++ b/scripts/Makefile.build
@@ -64,6 +64,11 @@ ifneq ($(hostprogs-y)$(hostprogs-m),)
 include scripts/Makefile.host
 endif
 
+# Do not include host rules unless needed
+ifneq ($(dtbo-y),)
+include scripts/Makefile.dtbo
+endif
+
 ifneq ($(KBUILD_SRC),)
 # Create output directory if not already present
 _dummy := $(shell [ -d $(obj) ] || mkdir -p $(obj))
diff --git a/scripts/Makefile.dtbo b/scripts/Makefile.dtbo
new file mode 100644
index 000000000000..db4a0f4b9a56
--- /dev/null
+++ b/scripts/Makefile.dtbo
@@ -0,0 +1,24 @@
+__dtbo := $(sort $(dtbo-y))
+
+dtbo-base	:= $(sort $(foreach m,$(__dtbo),$($(m)-base)))
+dtbo := $(foreach m,$(__dtbo),$(if $($(m)-base),$(m)))
+
+__dtbo     := $(addprefix $(obj)/,$(__dtbo))
+dtbo-base	:= $(addprefix $(obj)/,$(dtbo-base))
+dtbo	:= $(addprefix $(obj)/,$(dtbo))
+
+ifneq ($(DTC_OVERLAY_TEST_EXT),)
+DTC_OVERLAY_TEST = $(DTC_OVERLAY_TEST_EXT)
+quiet_cmd_dtbo_verify	= VERIFY  $@
+cmd_dtbo_verify = $(DTC_OVERLAY_TEST) $(addprefix $(obj)/,$($(@F)-base)) $@ $(dot-target).dtb
+else
+cmd_dtbo_verify = true
+endif
+
+$(obj)/%.dtbo: $(src)/%.dts FORCE
+	$(call if_changed_dep,dtc)
+	$(call if_changed,dtbo_verify)
+
+$(call multi_depend, $(dtbo), , -base)
+
+always +=  $(dtbo)
diff --git a/scripts/Makefile.lib b/scripts/Makefile.lib
index 861a2acd8cba..46881f329561 100644
--- a/scripts/Makefile.lib
+++ b/scripts/Makefile.lib
@@ -287,10 +287,16 @@ cmd_dt_S_dtb=						\
 $(obj)/%.dtb.S: $(obj)/%.dtb
 	$(call cmd,dt_S_dtb)
 
+ifneq ($(DTC_EXT),)
+DTC = $(DTC_EXT)
+else
+DTC = $(objtree)/scripts/dtc/dtc
+endif
+
 quiet_cmd_dtc = DTC     $@
 cmd_dtc = mkdir -p $(dir ${dtc-tmp}) ; \
 	$(CPP) $(dtc_cpp_flags) -x assembler-with-cpp -o $(dtc-tmp) $< ; \
-	$(objtree)/scripts/dtc/dtc -O dtb -o $@ -b 0 \
+	$(DTC) -O dtb -o $@ -b 0 \
 		-i $(dir $<) $(DTC_FLAGS) \
 		-d $(depfile).dtc.tmp $(dtc-tmp) ; \
 	cat $(depfile).pre.tmp $(depfile).dtc.tmp > $(depfile)
diff --git a/scripts/dtc/Makefile b/scripts/dtc/Makefile
index 2a48022c41e7..2eb4aec040f4 100644
--- a/scripts/dtc/Makefile
+++ b/scripts/dtc/Makefile
@@ -1,7 +1,9 @@
 # scripts/dtc makefile
 
 hostprogs-y	:= dtc
+ifeq ($(DTC_EXT),)
 always		:= $(hostprogs-y)
+endif
 
 dtc-objs	:= dtc.o flattree.o fstree.o data.o livetree.o treesource.o \
 		   srcpos.o checks.o util.o