device tree: enable gpio in kernel 3.18

Hey guys!

Can anybody share a simple example how to enable any of gpio pins available at BBB? I use kernel 3.18 and want to ass own dtsi file to the main am335x-bone.dts file to have a few gpio pins configured as GPIO In or Out imediately after the system boots.Tried a number of options but I don’t find files like these in /sys: