Any SoC chip register/bit funtion information for BPI-R4?

I know someone from BSD that is willing to look into this platform if there are chip register/bit function information for Filogic 880 on BPI-R4, then they can try to port OPNsense to it as well, currently they have some ports for like RPi 4, NanoPi R2S/R4S (RockChip RK3328/3399), not sure where I can get these?