mcp23s17gpio —
Driver for MCP23S17 gpio chip via SPI bus
mcp23s17gpio0 at spi? slave 0 flags 0
mcp23s17gpio1 at spi? slave 0 flags 1
mcp23s17gpio2 at spi? slave 0 flags 2
mcp23s17gpio3 at spi? slave 0 flags 3
gpio* at gpiobus?
The mcp23s17gpio driver supports up to 8 instances of
  the MCP23S17 16-bit GPIO chips. Access to the pins is provided by the
  gpio(4) interface. The
  mcp23s17gpio flags argument
  selects the hardware address of the chip instance.
The mcp23s17gpio driver first appeared in
  NetBSD 7.0.