reproduce:
        git checkout a24588245776dafc227243a01bfbeb8a59bafba9
        b4 shazam https://lore.kernel.org/r/20250409193004.643839-3-bjorn@kernel.org
        make menuconfig
        # enable CONFIG_COMPILE_TEST, CONFIG_WARN_MISSING_DOCUMENTS, CONFIG_WARN_ABI_ERRORS
        # install Sphinx 2.4.4
        make htmldocs