Basic Structure of b43 wireless driver

Hello everyone,

I am a student and I am doing a research to modify b43 wireless driver
for supporting APE Testbed. So I have to understand the structure of
b43 source code but it is really complicated with multiple files.
Please anyone can guide me!!! (For example: "what is the purpose of
each file or each function?" or "how I can read and understand these
codes?").

Thank you for your supporting.