Adding YANG model for TC_TO_DSCP_MAP (#21463)

issue : #20575

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#### Why I did it
"config-reload" in dualtor topologies were failing due to absence of TC_TO_DSCP Yang model.
The above failure was seen after the the PR sonic-net/sonic-utilities#3102

##### Work item tracking
- Microsoft ADO **(number only)**:

#### How I did it

#### How to verify it

Step-1: In DUT add the yang file to "/usr/local/yang-models/sonic-tc-dscp-map.yang" to this path.
Step-2: config reload -y

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#### Description for the changelog
Adding YANG model for TC_TO_DSCP_MAP along with test files.

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#### Link to config_db schema for YANG module changes
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Author: mssonicbld

src/sonic-yang-mgmt/sonic_yang_ext.py

@@ -18,7 +18,8 @@
     'DSCP_TO_FC_MAP_LIST',
     'EXP_TO_FC_MAP_LIST',
     'CABLE_LENGTH_LIST',
-    'MPLS_TC_TO_TC_MAP_LIST'
+    'MPLS_TC_TO_TC_MAP_LIST',
+    'TC_TO_DSCP_MAP_LIST'
 ]
 
 # Workaround for those fields who is defined as leaf-list in YANG model but have string value in config DB.

src/sonic-yang-models/setup.py

@@ -195,6 +195,7 @@ def run(self):
                          './yang-models/sonic-tc-priority-group-map.yang',
                          './yang-models/sonic-tc-queue-map.yang',
                          './yang-models/sonic-peer-switch.yang',
+                         './yang-models/sonic-tc-dscp-map.yang',
                          './yang-models/sonic-pfc-priority-queue-map.yang',
                          './yang-models/sonic-pfc-priority-priority-group-map.yang',
                          './yang-models/sonic-logger.yang',

src/sonic-yang-models/tests/files/sample_config_db.json

@@ -2268,6 +2268,17 @@
             }
         },
 
+        "TC_TO_DSCP_MAP": {
+           "tc_to_dscp_map1": {
+              "1": "1",
+              "2": "2"
+            },
+           "tc_to_dscp_map2": {
+              "3": "3",
+              "4": "4"
+            }
+        },
+
         "MAP_PFC_PRIORITY_TO_QUEUE": {
            "pfc_prio_to_q_map1": {
               "1": "1",

src/sonic-yang-models/tests/yang_model_tests/tests/qosmaps.json

@@ -109,5 +109,19 @@
     "PORT_QOS_MAP_APPLY_INVALID_PFC": {
         "desc": "Configure port pfc enable with invalid pfc priority.",
         "eStrKey": "Pattern"
+    },
+
+    "TC_TO_DSCP_MAP_CRETAE": {
+        "desc": "Configure a Traffic class to DSCP map."
+    },
+
+    "TC_TO_DSCP_MAP_CREATE_INVALID_TC": {
+        "desc": "Configure a Traffic class to DSCP with invalid key.",
+        "eStr": "Invalid Traffic Class"
+    },
+
+    "TC_TO_DSCP_MAP_CREATE_INVALID_DSCP": {
+        "desc": "Configure a Traffic class to DSCP map with invalid value.",
+        "eStr": "Invalid DSCP"
     }
 }

src/sonic-yang-models/tests/yang_model_tests/tests_config/qosmaps.json

@@ -855,6 +855,92 @@
                 ]
             }
         }
-    }
+    },
 
+    "TC_TO_DSCP_MAP_CRETAE": {
+        "sonic-tc-dscp-map:sonic-tc-dscp-map": {
+            "sonic-tc-dscp-map:TC_TO_DSCP_MAP": {
+                "TC_TO_DSCP_MAP_LIST": [
+                    {
+                        "name": "map1",
+                        "TC_TO_DSCP_MAP": [
+                            {
+                                "tc": "1",
+                                "dscp": "1"
+                            },
+                            {
+                                "tc":"2",
+                                "dscp":"2"
+                            },
+                            {
+                                "tc": "8",
+                                "dscp": "8"
+                            }
+                        ]
+                    },
+                    {
+                        "name": "map2",
+                        "TC_TO_DSCP_MAP": [
+                            {
+                                "tc": "1",
+                                "dscp": "1"
+                            },
+                            {
+                                "tc":"2",
+                                "dscp":"2"
+                            },
+                            {
+                                "tc": "8",
+                                "dscp": "8"
+                            }
+                        ]
+                    }
+                ]
+            }
+        }
+    },
+
+    "TC_TO_DSCP_MAP_CREATE_INVALID_TC": {
+        "sonic-tc-dscp-map:sonic-tc-dscp-map": {
+            "sonic-tc-dscp-map:TC_TO_DSCP_MAP": {
+                "TC_TO_DSCP_MAP_LIST": [
+                    {
+                        "name": "map3",
+                        "TC_TO_DSCP_MAP": [
+                            {
+                                "tc": "16",
+                                "dscp": "1"
+                            },
+                            {
+                                "tc":"2",
+                                "dscp":"2"
+                            }
+                        ]
+                    }
+                ]
+            }
+        }
+    },
+
+    "TC_TO_DSCP_MAP_CREATE_INVALID_DSCP": {
+        "sonic-tc-dscp-map:sonic-tc-dscp-map": {
+            "sonic-tc-dscp-map:TC_TO_DSCP_MAP": {
+                "TC_TO_DSCP_MAP_LIST": [
+                    {
+                        "name": "map3",
+                        "TC_TO_DSCP_MAP": [
+                            {
+                                "tc": "1",
+                                "dscp": "64"
+                            },
+                            {
+                                "tc":"2",
+                                "dscp":"2"
+                            }
+                        ]
+                    }
+                ]
+            }
+        }
+    }
 }

src/sonic-yang-models/yang-models/sonic-tc-dscp-map.yang

@@ -0,0 +1,67 @@
+module sonic-tc-dscp-map {
+
+    yang-version 1.1;
+
+    namespace "http://github.com/sonic-net/sonic-tc-dscp-map";
+
+    prefix tdm;
+
+    import sonic-types {
+        prefix stypes;
+    }
+
+    organization
+        "SONiC";
+
+    contact
+        "SONiC";
+
+    description
+        "TC_TO_DSCP_MAP yang Module for SONiC OS";
+
+    revision 2025-01-10 {
+        description
+            "Initial revision.";
+    }
+
+    container sonic-tc-dscp-map {
+
+        container TC_TO_DSCP_MAP {
+
+            description "TC_TO_DSCP_MAP part of config_db.json";
+
+            list TC_TO_DSCP_MAP_LIST {
+
+                key "name";
+
+                leaf name {
+                    type string {
+                        pattern '[a-zA-Z0-9]{1}([-a-zA-Z0-9_]{0,31})';
+                        length 1..32 {
+                            error-message "Invalid length for map name.";
+                            error-app-tag map-name-invalid-length;
+                        }
+                    }
+                }
+
+                list TC_TO_DSCP_MAP { //this is list inside list for storing mapping between two fields
+
+                    key "tc";
+
+                    leaf tc {
+                        type stypes:tc_type;
+                    }
+
+                    leaf dscp {
+                        type string {
+                            pattern "6[0-3]|[1-5][0-9]?|[0-9]?" {
+                                error-message "Invalid DSCP";
+                                error-app-tag dscp-invalid;
+                            }
+                        }
+                    }
+                }
+            }
+        }
+    }
+}