reproduce:
        git checkout 4176cf5c5651c33769de83bb61b0287f4ec7719f
        b4 shazam https://lore.kernel.org/r/20241214-nouveau-encoder-slave-v1-1-beda767472e3@linaro.org
        make menuconfig
        # enable CONFIG_COMPILE_TEST, CONFIG_WARN_MISSING_DOCUMENTS, CONFIG_WARN_ABI_ERRORS
        # install Sphinx 2.4.4
        make htmldocs