Context

I'm modifying GPIO drivers to get a feel for linux device drivers (after skimming over a few books).

• I'm hacking the xilinx gpio driver; I already got LEDs blinking (706 eval board, ARM32) with the base driver, so the hardware's setup & working.
• One of the hacks I did was changing { .compatible = "xlnx,xps-gpio-1.00.a", } to { .compatible = "xlnx,moogpio", }. I reflected this change in the device tree (which I checked via /proc/device-tree), however the GPIO does not seem to be loaded in /sys/class/gpio/
• changing the kernel debug flags (make menuconfig -> Kernel hacking -> printk and dmesg options) doesn't seem to give information on why it isn't being loaded.

Question

How does one debug why a driver isn't being loaded from a device tree?