reproduce:
        git checkout cee9395acd8043be0644b25c34bfa86623f2b935
        b4 shazam https://lore.kernel.org/r/0da43a8c-1755-49fe-b8e2-403489297f06@gmail.com
        make menuconfig
        # enable CONFIG_COMPILE_TEST, CONFIG_WARN_MISSING_DOCUMENTS, CONFIG_WARN_ABI_ERRORS
        # pip install -r Documentation/sphinx/requirements.txt
        make htmldocs