reproduce (this is a W=1 build):
        # https://github.com/frank-w/BPI-R2-4.14/commit/d6a0b75e787f1f174335d4164d7ebce4c7e576ee
        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 7.0-mt7622
        git checkout d6a0b75e787f1f174335d4164d7ebce4c7e576ee

        # save the config file
        mkdir build_dir && cp config build_dir/.config
        make W=1 O=build_dir ARCH=i386 olddefconfig
        make W=1 O=build_dir ARCH=i386 SHELL=/bin/bash drivers/net/dsa/mxl862xx/