I have been reading into this for some hours now, and it seems like I will need to write (or perhaps modify from some existing) DTB overlay or something like that?
I tried following the instructions here, and using a .dtbo file (hifiberry-amp100.dtbo) I copied from OSMC I have here on an RPi 3, but I don't think that's right as it mentions 'brcm,bcm2835' which I suppose means it can only be used with RPi.
The above mentioned .dtbo file seemed to be in some binary format, although I could still make out some text in it. I can't even seem to find the uncompressed (plain text) versions, I searched OSMC and HiFiBerry repos (amongst others), I don't think I am looking in right place (maybe I need to look in RPi Foundation or Linux kernel sources?).
Any help or pointers will be appreciated. This seems to be a non-trivial task (at least for a low to medium level wizard such as myself).