reproduce:
        git remote add anolis-intel-cloud https://gitee.com/anolis/intel-cloud-kernel.git
        git fetch --no-tags anolis-intel-cloud devel-5.10
        git checkout 88f66936c77127ed35d2e026e9a7bedf16385ff0
        make menuconfig
        # enable CONFIG_COMPILE_TEST, CONFIG_WARN_MISSING_DOCUMENTS, CONFIG_WARN_ABI_ERRORS
        # install Sphinx 2.4.4
        make htmldocs