=== dtb ===
The binary device tree, this is a file containing a description of the hardware in the device since phones don't have discoverable busses like x86 platforms. These are created from dts files in the kernel repository and produce a file called <code>zImage-dtb</code> for some Android kernels (older Android kernels do not generate a <code>dtb</code> file at all and have hardcoded the information directly in the kernel source). In mainline kernels, <code>dtb</code> files for all supported boards are created at once.
=== dri ===