ti-k3-r5-loader: support devicetree customization

This is duplicated from the U-Boot makefile & Kconfig.

Similarly to U-Boot custom boards sometimes need to adjust the U-Boot
devicetree. For example, the AM64x SDRAM controller supports inline ECC
which needs to be enabled in the R5 loader devicetree.

Please note that some versions of U-Boot have broken external devicetree
support and may require manual patching to build. See commit [1]
in the U-Boot tree.

[1] https://source.denx.de/u-boot/u-boot/-/commit/3609e1dc5f4d4c238dcd23e045ba6223310feffa

Signed-off-by: Patrick Oppenlander <patrick.oppenlander@gmail.com>
Signed-off-by: Gero Schwäricke <gero.schwaericke@grandcentrix.net>
[Romain: add gitlab URL]
Signed-off-by: Romain Naour <romain.naour@smile.fr>

boot/ti-k3-r5-loader/Config.in

@@ -95,6 +95,16 @@ config BR2_TARGET_TI_K3_R5_LOADER_CUSTOM_CONFIG_FILE
 	help
 	  Path to the TI K3 R5 Loader configuration file.
 
+config BR2_TARGET_TI_K3_R5_LOADER_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 arch/arm/dts/ before starting the
+	  build.
+
+	  To use this device tree source file, the U-Boot configuration
+	  file must refer to it.
+
 config BR2_TARGET_TI_K3_R5_LOADER_TIBOOT3_BIN
 	string "tiboot3.bin binary name"
 	default "tiboot3.bin"

boot/ti-k3-r5-loader/ti-k3-r5-loader.mk

@@ -88,7 +88,12 @@ define TI_K3_R5_LOADER_INSTALL_SWSFW_ITB
 	fi
 endef
 
+TI_K3_R5_LOADER_CUSTOM_DTS_PATH = $(call qstrip,$(BR2_TARGET_TI_K3_R5_LOADER_CUSTOM_DTS_PATH))
+
 define TI_K3_R5_LOADER_BUILD_CMDS
+	$(if $(TI_K3_R5_LOADER_CUSTOM_DTS_PATH),
+		cp -f $(TI_K3_R5_LOADER_CUSTOM_DTS_PATH) $(@D)/arch/arm/dts/
+	)
 	$(TARGET_CONFIGURE_OPTS) $(TI_K3_R5_LOADER_MAKE) -C $(@D) $(TI_K3_R5_LOADER_MAKE_OPTS)
 endef