Man pages matching name umad_register_oui in section 3:

umad_register_oui.3.en	debian 10 / libibumad-dev
umad_register_oui.3.en	debian 11 / libibumad-dev
umad_register_oui.3.en	debian 12 / libibumad-dev
umad_register_oui.3.en	debian 13 / libibumad-dev