It is a micro-controller...that is a microprocessor with memory built into it, for small tasks like operating an elevator or a very complicated washing machine.
See:
http://www.wvshare.com/datasheet/ATMEL_PDF/AT89S52.PDF
for a datasheet.
a family
89S52 has ISP so S stands for : Serial in System programmable.
It is a micro controller used in various applications of embedded systems
because in atmel .............it is easy to program and troubleshooting
S stands for serial
89s51 and 89s52 both are same version of 8051 microcontroller
8051 family
The 89S52 has four different ports. Each one of the ports has eight input/output lines. The ports are used to output data.
internal and external memory
I'm more of a PIC guy, but as far as i understood it, yes 8051 instruction set is the same for all 8051 legacy devices. That includes 89s52. You can find this out in device specific datasheet. For 89s52 it is written in a first row like this "Compatible with MCS®-51 Products".
c mos & smog
The EXT port in the PS4's Dual shock 4 controller is used as a extension port.