There's also a new book with many examples on using Device Trees on the new Beaglebone called "Bad to the Bone" http://www.morganclaypool.com/doi/abs/10.2200/S00500ED1V01Y201304DCS041. The ebook costs around $20. I believe hard copies can be bought for amazon for around $40. The book is very well written and covers DTO's as well as many aspects of Using the BBB's peripherals via bonescript/javascript and C. I highly recommend it.