Could someone point me to a guide / how to / existing build script to create a bootloader image for the Radxa Rock-3a?
Context...
I'm trying to get a Radxa Rock3c to boot with a modern (6x) Linux kernel. This has the Rockchip rx3566 unlike the Radxa Rock3a which has the rx3568 (supported by Armbian). This is my first time working with u-boot, so I'm trying to follow Rockchip's own guide (here). Sadly that guide seems to be a rather cryptic, poorly translated, and file names don't appear to mach anything I can find.
Radxa's own binaries (here) don't seem to know about the rk3566 or rk3568: I get errors when I use mkimage. But other distributions (Armbian and Alpine) have ready built mkimage that does know about rk3568 not rk3566. (Okay!). So my plan is to see if I can use mkimage from Armbian along with rk3566 binaries from Radxa's own repo. Even if I swing across to using the Rock3a I'll still want to be able to re-build the boot loader... so any information here is useful.
I'm currently stuck on how to configure / build "spl/u-boot-spl.bin" provided by u-boot source code. I don't see good instructions on that.
Long story short...
Armbian developers managed to make u-boot boot a Radxa Rock3a with a 6.x kernel. How did they do it.
[i don't mind reading source code, I just need to understand which bits were the Armbian customisations / configurations]