How to porting u-boot to my own board?

Another three questions.

1. Now I can run u-boot in sdram, but how can I know the hardware in my system are being initialized proper.

2. I have build vmlinux.bin. I want to run it in sdram through u-boot, how to do?(I find mkimage can not be used in my u-boot directory.)

3. Because I do not know clearly the detail of the nios2 application execution(for example--helloworld).

So I want to know it.

cpu initial->hardware initial->jump main app. What files(.S, .h, .c) do this involve? Which reference of nios2 is helpful to me to know this.

Thank you,

LiangYi