If you are set on using the 74C922 chip then connect the DataAvailable output to a port pin on the 8051. Have your software poll this pin. When the DataAvailable goes high to a "1" then the '922 has detected a key.

In order to see what key was pressed take the OutputEnable pin of the '922 and tie it to GND. Then connect the output A, B, C & D
pins to more port pins on the 8051. At the time when you see the DataAvailable go to a "1" simply have the 8051 program read the A/B/C/D pins into a register. These will be a 4-bit code that represents which switch that was detected by the '922. Look in the '922 data sheet to see what positions result in which code.

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The 74C922 chip is a really really old chip. If you have them in the necessary quantity then go for it if you wish. However these days most people connect the matrix of switches directly to the 8051 port pins and implement the function that is inside the '922 in 8051 software. Keypad scanning has been discussed here before in great detail. Try a search if you are interested.

I hope this helps
Michael Karas