Okay for anyone else that’s going down this road, I’ve put up the code I’ve used to get it working:
ATF: https://git.lumina-sensum.com/LuminaSensum/arm-trusted-firmware/commits/WIP_v2.3-LS
Barebox: https://git.lumina-sensum.com/LuminaSensum/barebox/commits/WIP_next-LS
Linux: https://git.lumina-sensum.com/LuminaSensum/linux/commits/WIP_v5.8-LS