linux/Documentation/acpi/i2c-muxes.txt

ACPI I2C Muxes
--------------

Describing an I2C device hierarchy that includes I2C muxes requires an ACPI
Device () scope per mux channel.

Consider this topology:

+------+   +------+
| SMB1 |-->| MUX0 |--CH00--> i2c client A (0x50)
|      |   | 0x70 |--CH01--> i2c client B (0x50)
+------+   +------+

which corresponds to the following ASL:

Device (SMB1)
{
    Name (_HID, ...)
    Device (MUX0)
    {
        Name (_HID, ...)
        Name (_CRS, ResourceTemplate () {
            I2cSerialBus (0x70, ControllerInitiated, I2C_SPEED,
                          AddressingMode7Bit, "^SMB1", 0x00,
                          ResourceConsumer,,)
        }

        Device (CH00)
        {
            Name (_ADR, 0)

            Device (CLIA)
            {
                Name (_HID, ...)
                Name (_CRS, ResourceTemplate () {
                    I2cSerialBus (0x50, ControllerInitiated, I2C_SPEED,
                                  AddressingMode7Bit, "^CH00", 0x00,
                                  ResourceConsumer,,)
                }
            }
        }

        Device (CH01)
        {
            Name (_ADR, 1)

            Device (CLIB)
            {
                Name (_HID, ...)
                Name (_CRS, ResourceTemplate () {
                    I2cSerialBus (0x50, ControllerInitiated, I2C_SPEED,
                                  AddressingMode7Bit, "^CH01", 0x00,
                                  ResourceConsumer,,)
                }
            }
        }
    }
}