reproduce (this is a W=1 build):
        # https://github.com/frank-w/BPI-R2-4.14/commit/f6261a83d9f211b58713bae33b28f274b6454612
        git remote add frank-w-bpi-r2-4.14 https://github.com/frank-w/BPI-R2-4.14
        git fetch --no-tags frank-w-bpi-r2-4.14 pr/214
        git checkout f6261a83d9f211b58713bae33b28f274b6454612

        # save the config file
        mkdir build_dir && cp config build_dir/.config
        make W=1 O=build_dir ARCH=um olddefconfig
        make W=1 O=build_dir ARCH=um SHELL=/bin/bash drivers/net/ethernet/mediatek/