The Device Tree is a data structure for describing hardware. Rather than hard coding every detail of a device into an operating system, many aspects of the hardware can be described in a data structure that is passed to the operating system at boot time. The device tree is used both by Open Firmware, and in the standalone Flattened Device Tree (FDT) form.
Device Trees are related to open firmware. It is often abbreviated as DT. They are a mechanism to pass hardware parameters to an OS from a boot loader. Device Trees are common on embedded PowerPC CPUs and more recently ARM CPUs. There is a lot of effort in the Linux kernel to support and use Device trees.
The main benefit is that one kernel binary may support many systems, even ones not conceived when the binary was built.
The device tree supports variable length data with keys, much like XML. Also, by itself, it does not define what the keys mean beyond a few standard details like an address, etc. For instance, it doesn't describe how a video controller entry should look. It is fairly detailed on CPU, memory and bus topologies.
References
- Device tree overview at devicetree.org.
- Device Trees at elinux.org.
- Xilinx device tree tutorial for the Zynq CPU (ARM Cortex-A9).
- Linux device tree documentation, including documentation on specific device parameters.
