The Ethernet is at least 10Mb/s, so you cant connect directly the port pins to microcontroller - the processing to do the Manchester coding would be very time consuming.
An Ethernel chip that supports PHY+MAC is ENC28J60 from Microchip, but you need to write the code for LLC and TCP/IP stack. I think you can find examples on the net for this. You will connect ENC28J60 to uC through SPI interface.
So, if you want a 1 chip solution, you would better search for microcontrollers with Ethernet interface, like ARM.