share: sysbuild: bootloader: add BOOTLOADER_CUSTOM option as choice

This configuration aims to auxiliate on including a custom
bootloader build when building using sysbuild.
Its build should be configured and triggered from the target's
sysbuild cmake files.

Signed-off-by: Almir Okato <[email protected]>

Author: almir-okato

share/sysbuild/image_configurations/MAIN_image_default.cmake

@@ -5,15 +5,16 @@
 # This sysbuild CMake file sets the sysbuild controlled settings as properties
 # on the main Zephyr image.
 
-set_config_bool(${ZCMAKE_APPLICATION} CONFIG_BOOTLOADER_MCUBOOT "${SB_CONFIG_BOOTLOADER_MCUBOOT}")
-set_config_string(${ZCMAKE_APPLICATION} CONFIG_MCUBOOT_SIGNATURE_KEY_FILE
-                  "${SB_CONFIG_BOOT_SIGNATURE_KEY_FILE}"
-)
-set_config_string(${ZCMAKE_APPLICATION} CONFIG_MCUBOOT_ENCRYPTION_KEY_FILE
-                  "${SB_CONFIG_BOOT_ENCRYPTION_KEY_FILE}"
-)
-
 if(SB_CONFIG_BOOTLOADER_MCUBOOT)
+  set_config_bool(${ZCMAKE_APPLICATION} CONFIG_BOOTLOADER_MCUBOOT y)
+
+  set_config_string(${ZCMAKE_APPLICATION} CONFIG_MCUBOOT_SIGNATURE_KEY_FILE
+                    "${SB_CONFIG_BOOT_SIGNATURE_KEY_FILE}"
+  )
+  set_config_string(${ZCMAKE_APPLICATION} CONFIG_MCUBOOT_ENCRYPTION_KEY_FILE
+                    "${SB_CONFIG_BOOT_ENCRYPTION_KEY_FILE}"
+  )
+
   if("${SB_CONFIG_SIGNATURE_TYPE}" STREQUAL "NONE")
     set_config_bool(${ZCMAKE_APPLICATION} CONFIG_MCUBOOT_GENERATE_UNSIGNED_IMAGE y)
   else()

share/sysbuild/images/bootloader/Kconfig

@@ -26,6 +26,13 @@ config BOOTLOADER_MCUBOOT
 	help
 	  Include MCUboot (Zephyr port) as the bootloader to use
 
+config BOOTLOADER_CUSTOM
+	bool "Custom bootloader"
+	help
+	  Include custom bootloader in the build
+	  (the bootloader build must be configured and triggered
+	  from the target SOC or BOARD sysbuild system)
+
 endchoice
 
 if BOOTLOADER_MCUBOOT