reproduce:
        git checkout next-20240416
        b4 shazam https://lore.kernel.org/r/25dd4334e3b37eaa628c20265841f251968c2b75.1713335916.git.lorenzo@kernel.org
        make menuconfig
        # enable CONFIG_COMPILE_TEST, CONFIG_WARN_MISSING_DOCUMENTS, CONFIG_WARN_ABI_ERRORS
        # install Sphinx 2.4.4
        make htmldocs