{
    "none": { }
}

{
    "433lirc": {
        "socket": "/dev/lirc0"
    }
}

note¹⁾

{
    "433gpio": {
        "sender": 1,
        "receiver": 0
    }
}

Before you can use the lirc_rpi kernel module, you have to run the following command (for kernels with disabled “Device tree support”):

sudo modprobe lirc_rpi gpio_in_pin=18 gpio_out_pin=17

To make sure this is done every reboot, edit /etc/modules and add the following line:

lirc_rpi gpio_in_pin=18 gpio_out_pin=17

If you have enabled “Device tree support” (since Raspbian with kernel 3.18 it's the default configuration), you have to add the following line to /boot/config.txt:

dtoverlay=lirc-rpi,gpio_in_pin=18,gpio_out_pin=17

This will load the module lirc_rpi, so you don't have to add lirc_rpi to /etc/modules or run sudo modprobe lirc_rpi.