boot/optee-os: add out-of-source OPTEE-OS device tree support

Similarly to U-Boot, this patch adds the ability to copy in and build
out-of-source device tree sources during an OPTEE-OS build. To build
the external device tree source file, the OP-TEE OS configuration must
refer to it with the CFG_EMBED_DTB_SOURCE_FILE option and no platform
flavor needs to be specified.

Signed-off-by: Kory Maincent <kory.maincent@bootlin.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>

boot/optee-os/Config.in

@@ -130,6 +130,17 @@ config BR2_TARGET_OPTEE_OS_PLATFORM_FLAVOR
 	  Value for the optional PLATFORM_FLAVOR build directive
 	  provided to OP-TEE OS.
 
+config BR2_TARGET_OPTEE_OS_CUSTOM_DTS_PATH
+	string "Device Tree Source file paths"
+	help
+	  Space-separated list of paths to device tree source files
+	  that will be copied to core/arch/arm/dts/ before starting the
+	  build.
+
+	  To use this device tree source file, the OP-TEE OS configuration
+	  must refer to it with the CFG_EMBED_DTB_SOURCE_FILE option and
+	  no platform flavor needs to be specified.
+
 config BR2_TARGET_OPTEE_OS_ADDITIONAL_VARIABLES
 	string "Additional build variables"
 	help

boot/optee-os/optee-os.mk

@@ -84,6 +84,8 @@ endif
 
 OPTEE_OS_IMAGE_FILES = $(call qstrip,$(BR2_TARGET_OPTEE_OS_CORE_IMAGES))
 
+OPTEE_OS_CUSTOM_DTS_PATH = $(call qstrip,$(BR2_TARGET_OPTEE_OS_CUSTOM_DTS_PATH))
+
 ifeq ($(BR2_TARGET_OPTEE_OS_CORE),y)
 define OPTEE_OS_BUILD_CORE
 	$(TARGET_MAKE_ENV) $(MAKE) -C $(@D) O=$(OPTEE_OS_BUILDDIR_OUT) \
@@ -120,6 +122,9 @@ endef
 endif # BR2_TARGET_OPTEE_OS_SDK
 
 define OPTEE_OS_BUILD_CMDS
+	$(if $(OPTEE_OS_CUSTOM_DTS_PATH),
+		cp -f $(OPTEE_OS_CUSTOM_DTS_PATH) $(@D)/core/arch/arm/dts/
+	)
 	$(OPTEE_OS_BUILD_CORE)
 	$(OPTEE_OS_BUILD_SDK)
 endef