having a look at https://gitlab.raptorengineering.com/kestrel-collaboration/kestrel-litex/litex-boards/-/blob/master/litex_boards/targets/rcs_arctic_tern_bmc_card.py#L121 begin adding support for rcs_arctic_tern_bmc_card to nmigen-boards, comparing that one with OrangeCrabR0_2_85k_Platform