Chapter 11 of STREAMS Modules and Drivers, UNIX SVR4.2 describes the Data Link Provider Interface (DLPI) as implemented using STREAMS facilities.
The IRIX networking support is not STREAMS-based, but rather is based on BSD ifnet architecture. This is discussed in Chapter 16, "Network Device Drivers." The IRIX network support includes DLPI support as an add-on feature to the ifnet driver interface. If you are porting a network device driver to IRIX, it is better to convert it to the ifnet interface. You can install a DLPI-based network device driver, but only other STREAMS modules could use it--there would be no connection to the rest of the IRIX networking system.