reproduce:
        git checkout da4f3b72c8831975a06eca7e1c27392726f54d20
        b4 shazam https://lore.kernel.org/r/20240903-rockchip-canfd-v4-1-1dc3f3f32856@pengutronix.de
        make menuconfig
        # enable CONFIG_COMPILE_TEST, CONFIG_WARN_MISSING_DOCUMENTS, CONFIG_WARN_ABI_ERRORS
        # install Sphinx 2.4.4
        make htmldocs