Where to put the source of a DD of a custom hardware.

Hi, I'm developing a device driver to drive a specific custom hardware, that is implemented in FPGA. Since it is an application specific device driver, where (in witch folder) should I put Its source in my local kernel source tree? Is there any guideline or best practice about it? This device driver is basically a character device, that copies stuff from hardware to kernel space and then from user space. Regards, Raphael