current state of BBB device tree source files?

i'm in the midst of writing an online tutorial on device tree source
files and, rather than just discuss generic files, i thought i'd use
BBB device tree .dts files as a working example.

  where would one keep up to date with the cutting edge of BBB device
tree files? currently, what i do is use OE and the meta-beaglebone
layer to build for a "beaglebone" machine, and just examine the dts
files created by the patching procedure you find under the directory

  what i get there are the files:

* am335x-boneblack.dts
* am33xx.dtsi
* am335x-bone-common.dtsi

and so on, and so on. they don't need to be the absolute cutting
edge, but they're clearly fairly recent.

  is there a better way to track device tree source files for the BBB?