Can we write drivers for unsupported WiFi cards in OS X?

I have an old laptop with a Qualcomm Atheros QCNFA435 WiFi card which as far as I know isn't supported in OS X. I looked on eBay for a compatible Broadcom card but all of them are like £25+, a price I'd be willing to avoid if possible for a WiFi card. I know I could just use HornDIS for tether WiFi with Android, but couldn't you write the drivers for unsupported cards if you had the knowledge and were willing to put in the efforts? Are there any good resources for OS X driver writing?