meta-rauc-nxp: added support for the FRDM i.MX 93 development board

Since the board layout is very similar to one of the products, the layer included,
the changes here are very minimalistics:
- Updated the README file
- Added a recipe for building out of meta-imx which does no build off linux-yocto

Signed-off-by: Ron Munitz <ron@thepscg.com>

Author: ronpscg

meta-rauc-nxp/README.rst

@@ -39,7 +39,7 @@ Actual requirements may differ from project to project and will
 probably need a much different RAUC/bootloader/system configuration.
 
 
-Currently this layer supports only cubox-i/HummingBoard boards.
+Currently this layer supports cubox-i/HummingBoard boards, and the FRDM-IMX93 development board.
 
 
 I. Adding the meta-rauc-nxp layer to your build
@@ -51,7 +51,7 @@ Run 'bitbake-layers add-layer meta-rauc-nxp'
 II. Build NXP Demo System
 ===============================================
 
-For Olimex iMX8MP-SOM-4GB-IND and iMX8MP-SOM-EVB-IND set in local.conf:
+For Olimex iMX8MP-SOM-4GB-IND and iMX8MP-SOM-EVB-IND set in local.conf::
 
     MACHINE = "olimex-imx8mp-evb"
     INIT_MANAGER = "systemd"
@@ -61,6 +61,9 @@ For Olimex iMX8MP-SOM-4GB-IND and iMX8MP-SOM-EVB-IND set in local.conf:
     IMAGE_FSTYPES:append = " ext4"
     IMAGE_BOOT_FILES:append = " boot.scr"
 
+For FRDM-IMX93 you would can use the exact same parameters as above (i.e., use the dual-imx-boot-bootpart.wks.in kickstart file), and use the following ``MACHINE``::
+    MACHINE = "imx93frdm"
+
 For cubox-i/HummingBoard follow the steps below:
 
 ::
@@ -157,3 +160,4 @@ A convenient way to host HTTP server is::
 
 After the update is complete reboot the board to boot from the updated rootfs.
 
+The steps for the iMX93 boards are identical, other than the file names. For example, should you build ``core-image-base`` (which is the default bundled image in all of the aforementioned products in this README fie), your will want to install ``update-bundle-imx93frdm.raucb`` and flash the corresponding ``.wic.zstd`` image name respectfully.

meta-rauc-nxp/recipes-kernel/linux/linux-imx_%.bbappend

@@ -0,0 +1,15 @@
+FILESEXTRAPATHS:prepend := "${THISDIR}/files:"
+SRC_URI += "file://rauc.cfg"
+
+# linux-imx from meta-imx/meta-imx-bsp does not inherit linux-yocto and does not implement the fragment mechanisms.
+# So we just add it and call merge-config manually, should one choose to use the iMX downstream recipe (rather than the community fsl one)
+do_configure:append() {
+	# ${S}: source ;  ${B}: build ; ${WORKDIR}: workdir (fragments go there via SRC_URI)
+	if [ -f "${WORKDIR}/rauc.cfg" ]; then
+		# We use the kernel's own script to ensure it's done right
+		${S}/scripts/kconfig/merge_config.sh -m -O ${B} ${B}/.config ${WORKDIR}/rauc.cfg
+
+		# This part ensures the .config is valid and dependencies are resolved
+		oe_runmake -C ${S} O=${B} oldconfig
+	fi
+}