MLKU-25-1 dt-bindings: crypto: fsl: add secure memory

This is a rework of the following i.MX BSP commit
(rel_imx_4.19.35_1.1.0_rc2):
0adf02011a49 ("MLK-18082: defconfig: Add caam to 7ulp conf")

Signed-off-by: Franck LENORMAND <franck.lenormand@nxp.com>
Signed-off-by: Horia Geantă <horia.geanta@nxp.com>

Documentation/devicetree/bindings/crypto/fsl-sec4.txt

@@ -202,6 +202,26 @@ EXAMPLE
 	};
 
 
+=====================================================================
+Secure memory (SM) Node
+
+  - compatible
+      Usage: required
+      Value type: <string>
+      Definition: Must include "fsl,imx6q-caam-sm"
+
+  - reg
+      Usage: required
+      Value type: <prop-encoded-array>
+      Definition: Specifies a two SM parameters:  an offset from
+          the parent physical address and the length the SM registers.
+
+EXAMPLE
+  caam_sm: caam-sm@100000 {
+    compatible = "fsl,imx6q-caam-sm";
+    reg = <0x100000 0x4000>;
+  };
+
 =====================================================================
 Run Time Integrity Check (RTIC) Node