[ONOS-3878] YANG Listeners methods for Module and SubModule

Change-Id: Ied2fcf631d302b26ef84af8e98895d8ccb6d6269
diff --git a/src/main/java/org/onosproject/yangutils/parser/impl/listeners/SubModuleListener.java b/src/main/java/org/onosproject/yangutils/parser/impl/listeners/SubModuleListener.java
new file mode 100644
index 0000000..25f2764
--- /dev/null
+++ b/src/main/java/org/onosproject/yangutils/parser/impl/listeners/SubModuleListener.java
@@ -0,0 +1,77 @@
+/*
+ * Copyright 2016 Open Networking Laboratory
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.onosproject.yangutils.parser.impl.listeners;
+
+import org.onosproject.yangutils.parser.antlrgencode.GeneratedYangParser;
+import org.onosproject.yangutils.parser.impl.TreeWalkListener;
+
+/*
+ * Reference: RFC6020 and YANG ANTLR Grammar
+ *
+ * ABNF grammar as per RFC6020
+ * submodule-stmt      = optsep submodule-keyword sep identifier-arg-str
+ *                             optsep
+ *                             "{" stmtsep
+ *                                 submodule-header-stmts
+ *                                 linkage-stmts
+ *                                 meta-stmts
+ *                                 revision-stmts
+ *                                 body-stmts
+ *                             "}" optsep
+ *
+ * ANTLR grammar rule
+ * submodule_stmt : SUBMODULE_KEYWORD IDENTIFIER LEFT_CURLY_BRACE submodule_body* RIGHT_CURLY_BRACE;
+ * submodule_body : submodule_header_statement linkage_stmts meta_stmts revision_stmts body_stmts;
+ */
+
+/**
+ * Implements listener based call back function corresponding to the "submodule"
+ * rule defined in ANTLR grammar file for corresponding ABNF rule in RFC 6020.
+ */
+public final class SubModuleListener {
+
+    /**
+     * Creates a new sub module listener.
+     */
+    private SubModuleListener() {
+    }
+
+    /**
+     * It is called when parser receives an input matching the grammar
+     * rule (sub module), perform validations and update the data model
+     * tree.
+     *
+     * @param listener Listener's object.
+     * @param ctx context object of the grammar rule.
+     */
+    public static void processSubModuleEntry(TreeWalkListener listener,
+                                             GeneratedYangParser.SubModuleStatementContext ctx) {
+        // TODO method implementation
+    }
+
+    /**
+     * It is called when parser exits from grammar rule (submodule), it perform
+     * validations and update the data model tree.
+     *
+     * @param listener Listener's object.
+     * @param ctx context object of the grammar rule.
+     */
+    public static void processSubModuleExit(TreeWalkListener listener,
+                                            GeneratedYangParser.SubModuleStatementContext ctx) {
+        // TODO method implementation
+    }
+}