initial buildroot for linux 5.15

board/kontron/smarc-sal28/readme.txt

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+Kontron SMARC-sAL28
+===================
+
+How to build it
+===============
+
+Configure Buildroot:
+
+  $ make kontron_smarc_sal28_defconfig
+
+Change settings to fit your needs (optional):
+
+  $ make menuconfig
+
+Compile everything and build the rootfs image:
+
+  $ make
+
+Copying the image to a storage device
+=====================================
+
+Buildroot builds an image which can be written to the internal eMMC
+storage, a SD card or an USB thumb drive. You can use the following
+command on your host:
+
+  $ sudo dd if=output/images/sdcard-emmc.img of=/dev/sdx bs=1M
+
+Where /dev/sdx is the corresponding block device of your SD card or USB
+thumb drive. To flash it on your internal eMMC use the following command on
+the board:
+
+  # dd if=sdcard-emmc.img of=/dev/mmcblk1 bs=1M
+
+Be sure you have not booted from the internal eMMC in this case!
+
+Booting the board
+=================
+
+By default the bootloader will search for the first valid image, starting
+with the internal eMMC. Consult the vendor documentation on how to use the
+DIP switches to select specific boot devices. To use the bootloader
+environment set the boot_targets correspondingly. E.g.:
+
+  # setenv boot_targets usb0
+
+To boot from an USB thumb drive.
+
+The device tree is loaded according to the filename in fdtfile. The
+following command will set the default device tree, which works on almost
+all variants (with less features of course):
+
+  # setenv fdtfile freescale/fsl-ls1028a-kontron-sl28.dtb
+
+Set this to a device tree which fits your board variant.
+
+Connect your serial cable to SER1 and open your favorite terminal emulation
+program (baudrate 115200, 8n1). E.g.:
+
+  $ picocom -b 115200 /dev/ttyUSB0
+
+You will get a warning reported by fdisk when you examine the SD card.
+This is because the genimage.cfg file doesn't specify the SD card size
+(as people will naturally have different sized cards), so the
+secondary GPT header is placed after the rootfs rather than at the end
+of the disk where it is expected to be.
+
+You will see something like this at boot time:
+
+[    4.552797] GPT:Primary header thinks Alt. header is not at the end of the disk.
+[    4.560237] GPT:266272 != 7864319
+[    4.563565] GPT:Alternate GPT header not at the end of the disk.
+[    4.569596] GPT:266272 != 7864319
+[    4.572925] GPT: Use GNU Parted to correct GPT errors.
+
+Updating the bootloader
+=======================
+
+Buildroot will automatically build the u-boot bootloader. The resulting
+image is called u-boot.rom and you can find it in the images/ directory.
+
+To update the bootloader on the board you could either copy it to an
+USB thumb drive or you could put it on a TFTP server. The following
+example assumes you have the bootloader image copied to the root of
+a thumb drive:
+
+  # usb start
+  # load usb 0:1 $loadaddr u-boot.rom
+  # sf probe 0 && sf update $fileaddr 0x210000 $filesize