==uboot bootup sequence==
http://www.51hei.com/mcu/1435.html


===stage 1===


boards.cfg -> armv7 -> arch/arm/cpu/armv7/start.S

===stage 2===
 arch/arm/lib/board.c

 board_init_f -> board_init_f -> ...(array)

 board_init_r


 arch_misc_init (usb)

==read==
http://blog.chinaunix.net/uid-28458801-id-3492939.html