reproduce:
        git remote add media-tree git://linuxtv.org/media_tree.git
        git fetch media-tree master
        git checkout media-tree/master
        b4 shazam https://lore.kernel.org/r/20230717020446.28877-4-herdler@nurfuerspam.de
        make menuconfig
        # enable CONFIG_COMPILE_TEST, CONFIG_WARN_MISSING_DOCUMENTS, CONFIG_WARN_ABI_ERRORS
        make htmldocs