the porting of Linux

Hi, all,
These days I am looking through the Linux ppc source code.
I am just wondering how much effort or what should be done
 if I want to port such code to a different platform, such as arm, or other
so specific one.
I know the arch-specific codes are located at linux/arch/... .
But I just want to know if there is exact interface specification
about the interfaces that the linux/arch/... must provide for the
arch-independent kernel codes.

Any suggestions and discussion is appreciated!
thanks a lot!

BRs
Rolf Liu


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