dt-bindings: arm: fsl: add TQMa8MxNL boards

TQMa8MxNL is a SOM family using NXP i.MX8MN[Q,QL,DL,S,SL] CPU
MBa8Mx is an evaluation mainbord for this SOM

The SOM needs a mainboard, therefore we provide two compatibles here:

"tq,imx8mn-<SOM>" for the module and
"tq,imx8mn-<SOM>-<SBC>" for mainboards
Signed-off-by: Alexander Stein <alexander.stein@ew.tq-group.com>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>

Documentation/devicetree/bindings/arm/fsl.yaml

@@ -818,6 +818,17 @@ properties:
           - const: variscite,var-som-mx8mn
           - const: fsl,imx8mn
 
+      - description:
+          TQMa8MxNL is a series of SOM featuring NXP i.MX8MN system-on-chip
+          variants. It is designed to be soldered on different carrier boards.
+          All variants (TQMa8M[Q,D,S][L]NL) use the same device tree, hence only
+          one compatible is needed.
+        items:
+          - enum:
+              - tq,imx8mn-tqma8mqnl-mba8mx # TQ-Systems GmbH i.MX8MN TQMa8MQNL SOM on MBa8Mx
+          - const: tq,imx8mn-tqma8mqnl     # TQ-Systems GmbH i.MX8MN TQMa8MQNL SOM
+          - const: fsl,imx8mn
+
       - description: i.MX8MP based Boards
         items:
           - enum: