Thanks for your reply. I'm reading hw/mips_r4k.c. But I found I should dive into the source code.
I'm looking for some big picture level document for add a new machine using a supported core.
It seems qemu consists 3 parts of code
1. The core dynamic translate engineer to support several archs, just like mips, arm, ppc....
2. The peripheral emulation pool.
3. The platform relative code, just like hw/mips_jazz.c ..., it just connect the arch and the peripherals according to the real board.
I think my work should be the 2 and 3. And I'd like to find some documents for them.