[U-Boot-Users] About creating patch for U-boot

Hi

i'm actually using U-Boot 1.1.2 on an AT91RM9200 based board and if changed few files to use an LXT971A Phy component instead of using the Phy Davicom component. So i would like to create a .patch file to put all my modifications on U-Boot 1.1.3. Can someone indicates me how can i do it?