Raj of Embedded Lab has writen an article about his latest project, an encoded 4×4 matrix keypad using MM74C922:
In this project, we are building a simplified 16-switch keypad using the MM74C922 encoder chip, which converts a key switch closure to a 4-bit nibble output.
This appears to be an EOL part with practically no availability from mainline distributers. It looks like you can get them on eBay, but you’re still paying $1 per chip — with all the slings and arrows that come from buying ebay parts direct from China. At that price, it is going to be cheaper to use a dedicated microcontroller. If you are already using a microcontroller, it would make a lot more sense to simply select one with enough pins to handle the keyboard.