In Linux everything is a file. That’s a good thing because it doesn’t matter what program language you use you can control the IO by writing to the appropriate file. The problem is ther are thousands of files on a Linux system. Is there a standard directory where the files created dy the device tree can de found? Any way of locating the files that are linked to a given pin number like P8_14? Any documentation on the device tree?
My recommendation would be for you to get the beaglebone black book by Derek Malloy. Since it is dated use the older images from that vintage this way the code will work out of the book. That book is an excellent starting point for embedded / SBC work.