Hey guys,
I had a similar scenario - I ended up writing a trivial driver with help from the guys on #beagle
that can be found here: https://gist.github.com/17twenty/6998348
You can diff my dtsi file against that in the kernel sources to see how it comes together.
If you are using device tree overlays I recommend watching and reading Derek Molloys material on it http://derekmolloy.ie/beaglebone/beaglebone-gpio-programming-on-arm-embedded-linux/
HTH,
Nick