Hi,
I'm not sure if this is what you are looking for exactly (I can't really tell what it is you're looking for by reading your post), but The Internet Wayback Machine Archive has an archive of a (now dead) website called "Let's Hack Arcade Games" that has quite a few tutorials on how to go about using the MAME debugger/disassembler to reverse engineer a machine/game, with a focus on the Z80 processor and Donkey Kong as an example.
https://web.archive.org/web/20161106154 ... .com/?p=18