dt-bindings: can: can-transceiver: Document new binding

Add documentation to describe usage of the new can-transceiver binding.
This new binding is applicable for any CAN device therefore it exists as
its own document.
Signed-off-by: Franklin S Cooper Jr <fcooper@ti.com>
Signed-off-by: Sekhar Nori <nsekhar@ti.com>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Faiz Abbas <faiz_abbas@ti.com>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>

Documentation/devicetree/bindings/net/can/can-transceiver.txt

+Generic CAN transceiver Device Tree binding
+------------------------------
+
+CAN transceiver typically limits the max speed in standard CAN and CAN FD
+modes. Typically these limitations are static and the transceivers themselves
+provide no way to detect this limitation at runtime. For this situation,
+the "can-transceiver" node can be used.
+
+Required Properties:
+ max-bitrate:	a positive non 0 value that determines the max
+		speed that CAN/CAN-FD can run. Any other value
+		will be ignored.
+
+Examples:
+
+Based on Texas Instrument's TCAN1042HGV CAN Transceiver
+
+m_can0 {
+	....
+	can-transceiver {
+		max-bitrate = <5000000>;
+	};
+	...
+};