As someone who has added support for a few boards to both U-Boot and Barebox, I really recommend looking at Barebox first. U-Boot does have support for more ar

As someone who has added support for a few boards to both U-Boot and Barebox, I really recommend looking at Barebox first. U-Boot does have support for more architectures and SoCs, but the Barebox code base is of _much_ higher quality. Also, the bourne-like shell is a pleasure to work with!