Add association between FabricAdapter and Port

As a course of implementing PortCollection and Port schemas,
this commit adds a new association to describe the links
between FabricAdapter and Port.

 - FabricAdapter may be "connected_to" one or more ports,
 - A port may also be "connecting" one or more items.

The generic associations of 'containing' and 'contained_by'
are considered, but they are for the physically "containing" items.

Related schemas are:

- https://redfish.dmtf.org/schemas/v1/Port.v1_8_0.json

```
       "Links": {
           "description": "The links to other resources that are related to this resource.",
            "properties": {
                "AssociatedEndpoints": {
                    "description": "An array of links to the endpoints at the other end of the link.",
                    "items": {
                        "$ref": "http://redfish.dmtf.org/schemas/v1/Endpoint.json#/definitions/Endpoint"
                    },
                    "longDescription": "This property shall contain an array of links to resources of type Endpoint that represent the endpoints to which this port is connected.",
                    "readonly": true,
                    "type": "array"
                },
                "AssociatedEndpoints@odata.count": {
                    "$ref": "http://redfish.dmtf.org/schemas/v1/odata-v4.json#/definitions/count"
                },
```

- https://redfish.dmtf.org/schemas/v1/FabricAdapter.v1_5_0.json

```
                "Ports": {
                    "$ref": "http://redfish.dmtf.org/schemas/v1/PortCollection.json#/definitions/PortCollection",
                    "description": "The link to the collection of ports that exist on the fabric adapter.",
                    "longDescription": "This property shall contain a link to a Resource Collection of type PortCollection.",
                    "readonly": true
                },
```

Change-Id: I2cc8caf0128bf1cfa619312e689fe02039977e44
Signed-off-by: Myung Bae <myungbae@us.ibm.com>
diff --git a/yaml/xyz/openbmc_project/Inventory/Item/FabricAdapter.interface.yaml b/yaml/xyz/openbmc_project/Inventory/Item/FabricAdapter.interface.yaml
index 315f6bb..cd3cf91 100644
--- a/yaml/xyz/openbmc_project/Inventory/Item/FabricAdapter.interface.yaml
+++ b/yaml/xyz/openbmc_project/Inventory/Item/FabricAdapter.interface.yaml
@@ -2,3 +2,12 @@
     Implement to provide fabric adapter attributes. A physical fabric adapter
     capable of connecting to an interconnect fabric. Examples include but are
     not limited to Ethernet, NVMe over Fabrics, etc.
+
+associations:
+    name: connecting
+    description: >
+        Objects that implement FabricAdapter can optionally implement the
+        connecting association to  provide links to one or more Ports.
+    reverse_name: connected_to
+    required_endpoint_interfaces:
+        - xyz.openbmc_project.Inventory.Connector.Port