arch_minor_rev
mhu->minor = readl_relaxed_bitfield(&mhu->recv->aidr, struct aidr_t, arch_minor_rev);
u32 arch_minor_rev : 4;
mhu->minor = readl_relaxed_bitfield(&mhu->send->aidr, struct aidr_t, arch_minor_rev);
mhu->minor = readl_relaxed_bitmask(&mhu->ctrl->aidr, arch_minor_rev);