Custom peripheral

Hello,

I would like to create my own NIOS II peripheral. It is a kind of UART with registers such as Tx, Rx, Status and Control. Then this peripheral should transmit the Tx register or inform the NIOS II that Rx can be read. This peripheral would have an IRQ too.

The first thing that I want to do is to link this custom peripheral with the NIOS II core. I need an hardware interface (perhaps the Avalon interface ? or another one if it is easier) to access the peripheral registers and a software interface to write or read these registers.

Where can I find information on how to link this peripheral with the NIOS II (Hardware interface and software interface) ?

I think I need something which explains how to see my peripheral in SOPC Builder too if this is possible.

Thank you for your answers,

Jean LEE