In message 003a01c62026$958930c0$9e01120a@bilisim.local you wrote:

...

when modifying u-boot for a custom design board, is schematic of the board is required?

This depends on the quality and level of datail of the other documen- tation you have. I prefer to be able to verify this form the schematics (which usually is more up-to-date than all text docs, too).

i have datasheet of the board that explain memory map, bridge and cpu type, ex. is this datasheet sufficient to modify u-boot?

Maybe, maybe not. I don't know your board. Does your documentation explain the use of all port pins, clock routing, how to reset the PHY etc.?

if schematic is required, what are names of u-boot source files that must be modifyed according to schematic?

It depends...

Best regards,

Wolfgang Denk