reproduce:
        # https://git.kernel.org/pub/scm/linux/kernel/git/lee/leds.git/commit/?id=974d724e58fd2eee0fe46299901deae6fa9ebad1
        git remote add lee-leds https://git.kernel.org/pub/scm/linux/kernel/git/lee/leds.git
        git fetch --no-tags lee-leds for-leds-next
        git checkout 974d724e58fd2eee0fe46299901deae6fa9ebad1
        make menuconfig
        # enable CONFIG_COMPILE_TEST, CONFIG_WARN_MISSING_DOCUMENTS, CONFIG_WARN_ABI_ERRORS
        # pip install -r Documentation/sphinx/requirements.txt
        make htmldocs