I am reading the source code of coreboot, how do I understand the functions

[Jianmin Pan]

I am a newbie to coreboot, I am wondering is there an easy approach to
understand the functions.
For instance, when I am reading fallback_boot.c, it's very difficult for me
to understand such functions as inb(), outb(),RTC_PORT().
The method I am using now is to grep the function name and find out which
file it is in. Then read it. However, I still feel inconvenient.
I am used to use vim.
So, anybody have good suggestions?