[U-Boot-Users] the question about the Flat Device Tree on MPC8360?

HI, friends.

I want to update my linux version from 2.6.11 to 2.6.22 on MPC8360 board, I always fail when the linux version is about 2.6.11. Someone told me that I need to build the Flat Device Tree. I see that the U-boot-1.2.0 has one FDT command, but I did not know how to use this command and how to use the Flat Device Tree. I once see a document from freescale that the FDT file need tftp download to DDR memory first then bootm the linux. What's that FDT file? how can i get it? which DDR address that I need to tftp download? What is the FDT? Could someone teach me? Thanks.