[U-Boot] Add filesystem support

Hi all, I would say in advance: I am a new bye in the world of boot loader, and I can say things which does not make sense, after all I am here to ask !! :-)

I am working on an embedded system which we would like upgrade using a new filesystem YAFFS2 instead of the old JFFS2, we actually mount the JFFS2 partition from U-Boot and then we start the kernel. I looked in the boot source tree we actually use and I did not find YAFFS2 (or UBIFS ..) under the fs/ folder, then I assume I don't have it. I'd like add that support without update the whole uboot source tree, is it possible or is too much complicated ?

Thanks in advance,

Pietro.