What are the steps involved in porting an Arduino library?
I did essentially the same thing with getting the Adafruit ST7735 library working in chipKIT. I started a support thread here which can lead you through my process.

I tackled it the same way I do general programming:
1-» Copy over Libraries, get it so your compiler can actually SEE them.
2-» Start trying to compile and then triage errors from the "top level" down:
3-» Look for stlib functions you recognize as should be working and fix those.
4-» Look for AVR specific code and comment those out. I normally also add my initials and a comment: ckck - bitbanging SPI, so I can search for these later.
Repeat 3 and 4 until it works or you quit. :)

Reach out to the forums for your target; they might have been there done that -- or like in my case, you introduce them to something that they want, so they dive in and help.