040000 tree d4c5dd2d60db54e5c66f35a6f1d8672b49dd4dd6	boot_serial
040000 tree d13b5b4bd218cd93da0d3b88f95a10a8818d6a23	bootutil
040000 tree 2489adcd65c9000958e3aa01802a6a01817f5f99	mynewt
040000 tree c1962c4d9c1dbda4b3d829e7369ea7aa7c756d2b	zephyr