I just scanned the Broadcom Arm documention (thanks very much for that) and a couple of things stood out.
First, which pins are actually brought out to the GPIO interface?
Second, on page 160, it says "I2C slave only operation". Did I miss something or is this categorical--only I2C slave operation for the r-pi? I see some indication of 2 I2C interfaces, but couldn't get them clear in my mind.
Third, on page 175, a second UART is mentioned. Is the one brought out on the GPIO pins the console "mini-UART"? In the GPIO alternate function table, p.102 and following, it shows that TXD1 and RXD1 (apparently the second UART) are available as the ALT5 function mode for gpio pins 32 and 33. Are these pins brought out to the exposed GPIO header area? If they are available, can they be enabled by an ordinary program, or is special magic required?