Yes, you can upgrade the kernel on sysimage-v3 normally via apt upgrade. This works because we configured apt such that it will use our own patched kernel package from Index of /reform-debian-repo/ This all works via mechanisms that are already present in Debian – we are not adding any reform specific magic to the Debian package to allow upgrading. The only changes we make to the Debian linux kernel packaging is to add the reform-specific driver patches and skip building kernel packages that are irrelevant for the reform to reduce build time (like the cloud kernel image, for example). So don’t think that you have to port any “update functionality” from our patched kernel to arch. The only thing you have to port over are the reform-specific driver patches which you can find here: linux/patches · main · Reform / reform-debian-packages · GitLab together with this device tree definition: linux/imx8mq-mnt-reform2.dts · main · Reform / reform-debian-packages · GitLab
By default Arch tries to just install new kernel to /boot. By “port” I meant some sort of kernel-mnt-reform package that replaces standart kernel.
Yes, we do the same in Debian. Currently, u-boot in sysimage-v3 expects a boot.scr script which will then load the actual kernel (and optionally initrd). In Debian we use the software flash-kernel to generate that boot.scr. But the u-boot version in git implements distro_bootcmd support which will additionally support reading an extlinux.conf which might be easier to generate for you.
I have no clue about Arch but I can tell you anything about what we do in Debian in case you have any direct questions.
Oh, it seems I need to study how u-boot works.
Arch makes new Linux initramfs file every kernel package update just as Debian probably. I would probably just reuse Debian kernel and pack it as AUR package.
Will try!