reproduce:
        git checkout 40384c840ea1944d7c5a392e8975ed088ecf0b37
        b4 shazam https://lore.kernel.org/r/20241206172735.4310-4-towinchenmi@gmail.com
        make menuconfig
        # enable CONFIG_COMPILE_TEST, CONFIG_WARN_MISSING_DOCUMENTS, CONFIG_WARN_ABI_ERRORS
        # install Sphinx 2.4.4
        make htmldocs