dts: Add support for adding DT overlays in u-boot.img

If u-boot.img is a FIT image, CONFIG_OF_OVERLAY_LIST can be used to add
DT overlays to u-boot.img.
Signed-off-by: NJean-Jacques Hiblot <jjhiblot@ti.com>
Reviewed-by: NSimon Glass <sjg@chromium.org>

Makefile

@@ -1292,7 +1292,8 @@ MKIMAGEFLAGS_u-boot.img = -f auto -A $(ARCH) -T firmware -C none -O u-boot \
 	-a $(CONFIG_SYS_TEXT_BASE) -e $(CONFIG_SYS_UBOOT_START) \
 	-p $(CONFIG_FIT_EXTERNAL_OFFSET) \
 	-n "U-Boot $(UBOOTRELEASE) for $(BOARD) board" -E \
-	$(patsubst %,-b arch/$(ARCH)/dts/%.dtb,$(subst ",,$(CONFIG_OF_LIST)))
+	$(patsubst %,-b arch/$(ARCH)/dts/%.dtb,$(subst ",,$(CONFIG_OF_LIST))) \
+	$(patsubst %,-b arch/$(ARCH)/dts/%.dtbo,$(subst ",,$(CONFIG_OF_OVERLAY_LIST)))
 else
 MKIMAGEFLAGS_u-boot.img = -A $(ARCH) -T firmware -C none -O u-boot \
 	-a $(CONFIG_SYS_TEXT_BASE) -e $(CONFIG_SYS_UBOOT_START) \

dts/Kconfig

@@ -130,6 +130,14 @@ config OF_LIST
 	  device tree files (without the directory or .dtb suffix)
 	  separated by <space>.
 
+config OF_OVERLAY_LIST
+	string "List of device tree overlays to include for DT control"
+	depends on SPL_LOAD_FIT_APPLY_OVERLAY
+	help
+	  This option specifies a list of device tree overlays to use for DT
+	  control. This option can then be used by a FIT generator to include
+	  the overlays in the FIT image.
+
 choice
 	prompt "OF LIST compression"
 	depends on MULTI_DTB_FIT