reproduce:
        # https://git.kernel.org/pub/scm/linux/kernel/git/morse/linux.git/commit/?id=2132c4b5412b53caf5b353ae75e463adbc36a2e5
        git remote add morse https://git.kernel.org/pub/scm/linux/kernel/git/morse/linux.git
        git fetch --no-tags morse mpam/abmc/v6
        git checkout 2132c4b5412b53caf5b353ae75e463adbc36a2e5
        make menuconfig
        # enable CONFIG_COMPILE_TEST, CONFIG_WARN_MISSING_DOCUMENTS, CONFIG_WARN_ABI_ERRORS
        # install Sphinx 2.4.4
        make htmldocs