Add comment in ISerialization.h

src/DataTypes/Serializations/ISerialization.h

@@ -241,6 +241,9 @@ public:
     {
         SubstreamPath path;
         bool position_independent_encoding = true;
+        /// If set to false, don't enumerate dynamic subcolumns
+        /// (such as dynamic types in Dynamic column or dynamic paths in JSON column).
+        /// It may be needed when dynamic subcolumns are processed separately.
         bool enumerate_dynamic_streams = true;
     };