reproduce:
        git remote add lwn git://git.lwn.net/linux.git
        git fetch lwn docs-next
        git checkout lwn/docs-next
        b4 shazam https://lore.kernel.org/r/4478ae7ad952117a76b648ee2db7f8f92775ddf7.1769511207.git.hverkuil+cisco@kernel.org
        make menuconfig
        # enable CONFIG_COMPILE_TEST, CONFIG_WARN_MISSING_DOCUMENTS, CONFIG_WARN_ABI_ERRORS
        # pip install -r Documentation/sphinx/requirements.txt
        make htmldocs