reproduce:
        # https://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm.git/commit/?id=54ce12887d4a1d605f6a9b4736d07564ed07b529
        git remote add rafael-pm https://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm.git
        git fetch --no-tags rafael-pm bleeding-edge
        git checkout 54ce12887d4a1d605f6a9b4736d07564ed07b529
        make menuconfig
        # enable CONFIG_COMPILE_TEST, CONFIG_WARN_MISSING_DOCUMENTS, CONFIG_WARN_ABI_ERRORS
        # pip install -r Documentation/sphinx/requirements.txt
        make htmldocs