The Kindle Paperwhite has an internal serial port. I did a small modification to have it on the outside for easy root access on the go.
Did this the second time now. This time with my own Kindle. It's getting better every time. :)
I will update the instructions with proper names of everything and add more photos later.
Open the front of the kindle with a pry tool or a guitar pick.
Remove the 10 screws to get to the back side.
Remove the battery with it's 3 screws.