reproduce:
        git checkout ffd294d346d185b70e28b1a28abe367bbfe53c04
        b4 shazam https://lore.kernel.org/r/20250318-leds-tps6131x-v2-2-bc09c7a50b2e@emfend.at
        make menuconfig
        # enable CONFIG_COMPILE_TEST, CONFIG_WARN_MISSING_DOCUMENTS, CONFIG_WARN_ABI_ERRORS
        # install Sphinx 2.4.4
        make htmldocs