reproduce:
        git remote add anolis-intel-cloud https://gitee.com/anolis/intel-cloud-kernel.git
        git fetch --no-tags anolis-intel-cloud devel-6.6
        git checkout 2e953dfef122e371d4ab9778ad628e9a18c78827
        make menuconfig
        # enable CONFIG_COMPILE_TEST, CONFIG_WARN_MISSING_DOCUMENTS, CONFIG_WARN_ABI_ERRORS
        # install Sphinx 2.4.4
        make htmldocs