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 0ebb438216c3881f28b16c9e29df4f27e1a4c50f
        make menuconfig
        # enable CONFIG_COMPILE_TEST, CONFIG_WARN_MISSING_DOCUMENTS, CONFIG_WARN_ABI_ERRORS
        # install Sphinx 2.4.4
        make htmldocs