Build firmware for a riverbed SDI-AP5-B020

I found 2 old APs. one ocedo koala which I successfully flashed with community help:

the other one is a riverbed SDI-AP5-B020. looks like riverbed acquired ocedo and iterated a new model with new model number and the same exterior design.

because it's not officially supported by openWrt, I'd like to build initramfs-kernel.bin and squashfs-sysupgrade.bin myself, test it and commit it.

I have software build experience but I don't know how to collect hardware info like CPU, Package architecture, Taget, Subtarget etc.

how do I go about this?

I can use koala's initramfs-kernel.bin tftp boot the riverbed AP and ssh to it. can I use busybox commands to find out more hardware info?

https://openwrt.org/docs/guide-developer/adding_new_device
https://openwrt.org/docs/guide-developer/add.new.device

@tmn505 mentioned some important points in the other thread:

Can you get the boot / kernel log for the original firmware?