IVGCVSW-2992 Document Concat layer rename

Change-Id: I499591ef268f8da8e08f22fd25eaf5e6c6caf5d9
Signed-off-by: Jim Flynn <jim.flynn@arm.com>
diff --git a/src/armnnSerializer/SerializerSupport.md b/src/armnnSerializer/SerializerSupport.md
index 832c1a7..734ae18 100644
--- a/src/armnnSerializer/SerializerSupport.md
+++ b/src/armnnSerializer/SerializerSupport.md
@@ -10,6 +10,7 @@
 * Addition
 * BatchToSpaceNd
 * BatchNormalization
+* Concat
 * Constant
 * Convolution2d
 * DepthwiseConvolution2d
@@ -26,7 +27,6 @@
 * Maximum
 * Mean
 * Merge
-* Concat
 * Minimum
 * Multiplication
 * Normalization
@@ -45,3 +45,7 @@
 * Switch
 
 More machine learning layers will be supported in future releases.
+
+Note: Merger layer has been renamed Concat. Serializations of the old
+      format with Merger layers will deserialize to Concat layers to
+      maintain backward compatibility.
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