mips asm questions

[loody]

Dear all:
I have some questions about mips code:
1. what is LEAF and NESTED used for? The macro define of them seems
the same except the frame size.
what is that used for?
2. when I trace kernel code I find there are a lot assembly directory
which are not defined in as document, even in the section of mips
depend.
  Would anyone tell me where I can find the document that explain them all?
appreciate your help,
miloody