ANDROID: ARM: add config option to build zImage/dtb combo

Allows a defconfig to set a default dtb to concatenate with a zImage
to create a zImage-dtb.<dtb name>

Signed-off-by: Erik Gilling <konkers@android.com>
Change-Id: I34b643b1c49228fbae88a56e46c93c478089620d
diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index 88830c1..2656c66 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -1873,6 +1873,21 @@
 	  This was deprecated in 2001 and announced to live on for 5 years.
 	  Some old boot loaders still use this way.
 
+config BUILD_ARM_APPENDED_DTB_IMAGE
+	bool "Build a concatenated zImage/dtb by default"
+	depends on OF
+	help
+	  Enabling this option will cause a concatenated zImage and DTB to
+	  be built by default (instead of a standalone zImage.)  The image
+	  will built in arch/arm/boot/zImage-dtb.<dtb name>
+
+config BUILD_ARM_APPENDED_DTB_IMAGE_NAME
+	string "Default dtb name"
+	depends on BUILD_ARM_APPENDED_DTB_IMAGE
+	help
+	  name of the dtb to append when building a concatenated
+	  zImage/dtb.
+
 # Compressed boot loader in ROM.  Yes, we really want to ask about
 # TEXT and BSS so we preserve their values in the config files.
 config ZBOOT_ROM_TEXT
diff --git a/arch/arm/Makefile b/arch/arm/Makefile
index 6be9ee1..0ff187a 100644
--- a/arch/arm/Makefile
+++ b/arch/arm/Makefile
@@ -298,6 +298,8 @@
 # Default target when executing plain make
 ifeq ($(CONFIG_XIP_KERNEL),y)
 KBUILD_IMAGE := xipImage
+else ifeq ($(CONFIG_BUILD_ARM_APPENDED_DTB_IMAGE),y)
+KBUILD_IMAGE := zImage-dtb.$(CONFIG_BUILD_ARM_APPENDED_DTB_IMAGE_NAME)
 else
 KBUILD_IMAGE := zImage
 endif