reproduce:
        # https://git.kernel.org/pub/scm/linux/kernel/git/abelloni/linux.git/commit/?id=96a77ec577d4117f13e2527c9a377d6ba637f5c0
        git remote add abelloni https://git.kernel.org/pub/scm/linux/kernel/git/abelloni/linux.git
        git fetch --no-tags abelloni rtc-next
        git checkout 96a77ec577d4117f13e2527c9a377d6ba637f5c0
        make menuconfig
        # enable CONFIG_COMPILE_TEST, CONFIG_WARN_MISSING_DOCUMENTS, CONFIG_WARN_ABI_ERRORS
        # pip install -r Documentation/sphinx/requirements.txt
        make htmldocs