reproduce:
        git checkout f45acf7acf75921c0409d452f0165f51a19a74fd
        b4 shazam https://lore.kernel.org/r/20230929181616.2769345-3-adrian.larumbe@collabora.com
        make menuconfig
        # enable CONFIG_COMPILE_TEST, CONFIG_WARN_MISSING_DOCUMENTS, CONFIG_WARN_ABI_ERRORS
        # install Sphinx 2.4.4
        make htmldocs