dt-bindings: media: i2c: Add bindings for IMI RDACM20

The IMI RDACM20 is a Gigabit Multimedia Serial Link (GMSL) camera
capable of transmitting video and I2C control messages on a coax cable
physical link for automotive applications.

Document its device tree binding interface.

Signed-off-by: Jacopo Mondi <jacopo+renesas@jmondi.org>
Signed-off-by: Kieran Bingham <kieran.bingham+renesas@ideasonboard.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

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v2:
 - Provide imi vendor prefix
 - Fix minor spelling

v3:
 - update binding descriptions

v4:
 - No change

v5:
 - Specify optional third reg address for the MCU
2 files changed