[U-Boot] why the u-boot have no upload command?or there is another way to upload data to host?

hi all:

I do like to ask a question, why u-boot have no upload command? image such a scene: you have two board, and develop with one, but to some unknow reason, the board cannot boot. maybe it is the hardware problem, you want to upload all the data---a bin file, and download it to another board.

maybe tftp should the upload function? or there is another way to upload data to host?

thanks for reading!