of: documentation: add bindings documentation for TS-7970

This adds the documentation for the TS-7970 by Technologic Systems.
Signed-off-by: NSebastien Bourdelin <sebastien.bourdelin@savoirfairelinux.com>
Reviewed-by: NRob Herring <robh@kernel.org>
Signed-off-by: NShawn Guo <shawnguo@kernel.org>

Documentation/devicetree/bindings/arm/technologic.txt

@@ -10,3 +10,9 @@ It can be mounted on a carrier board providing additional peripheral connectors.
 Required root node properties:
 	- compatible = "technologic,imx6dl-ts4900", "fsl,imx6dl"
 	- compatible = "technologic,imx6q-ts4900", "fsl,imx6q"
+
+TS-7970 is a System-on-Module based on the Freescale i.MX6 System-on-Chip.
+It can be mounted on a carrier board providing additional peripheral connectors.
+Required root node properties:
+	- compatible = "technologic,imx6dl-ts7970", "fsl,imx6dl"
+	- compatible = "technologic,imx6q-ts7970", "fsl,imx6q"