Check the  official [Raspberry Pi documentation][1] on this topic. 

device tree source files (.dts) are *compiled* with [dtc][2] (device tree compiler) to flattened device tree BLOBs (.dtb files). Such .dtb files can be read and manipulated by the flattened device tree library **libfdt** - which is part of the dtc project too.

To install all necessary stuff on Debian/Ubuntu/Raspbian :

    sudo apt-get install device-tree-compiler libfdt-dev

The **source files** for the Pi-specific .dts files are part of the Linux kernel source tree under [/arch/arm/boot/dts][3]. [Example.][4] 



Last but not least the most experience on ATAGS parsing on the Pi is probably concentrated in the [bare metal forum on raspberrypi.org][5].


  [1]: https://www.raspberrypi.org/documentation/configuration/device-tree.md
  [2]: https://git.kernel.org/pub/scm/utils/dtc/dtc.git
  [3]: https://github.com/raspberrypi/linux/tree/rpi-4.9.y/arch/arm/boot/dts
  [4]: https://github.com/raspberrypi/linux/blob/rpi-4.9.y/arch/arm/boot/dts/bcm2708-rpi-b.dts
  [5]: https://www.raspberrypi.org/forums/viewforum.php?f=72