[U-Boot-Users] "How to trim the U-boot for IBM PPC 405EP board"

Hi All, I am newbie to U-boot. I am planning to use u-boot for my customized IBM PPC 405 EP board. Which includes spartan3s FPGA,89LPC932 controller,GM2120 Genesis chip,4MB Flash,32 MB SDRAM. Can you please help me in trimming the uboot ver 1.0.0. Which is the first file that gets executed at power on the board. I am going through the source code,but i am in a bit confusion to figure out the flow of u-boot files.

Thanks in Advance, Nag