I've just done a TV remote control receiver and it wasn't too difficult. There are some pretty good web sites that google will find.

The first thing you need is a receiver with built in demodulator. Most IR remote controls modulate the IR at 36 to 40kHz so that sunlight can be rejected. There's no benefit in trying to get the 8051 to do the demodulation.

I wired up the demodulated signal to a timer capture input, which I set to capture the active (falling) edges. Most remotes (except Sony) use a pulse frequency modulation scheme, so I set the ISR to look for periods above 1.65msec for '1' bits and below 1.65 msec for '0' bits. There are some start and repeat sections which use long pulses, but you may need to look at the data on an oscilloscope to see what youre getting. The '1's and '0's are transmitted LSB first as 32 bits or 4 bytes. The usual format is:
Manufacturers code byte
Device code byte
Key press code byte
Checksum parity byte