update docs for upstream service in foreign namespace

Author: haywoodsh

content/nic/configuration/virtualserver-and-virtualserverroute-resources.md

@@ -333,7 +333,7 @@ tls:
 |Field | Description | Type | Required |
 | ---| ---| ---| --- |
 |``name`` | The name of the upstream. Must be a valid DNS label as defined in RFC 1035. For example, ``hello`` and ``upstream-123`` are valid. The name must be unique among all upstreams of the resource. | ``string`` | Yes |
-|``service`` | The name of a [service](https://kubernetes.io/docs/concepts/services-networking/service/). The service must belong to the same namespace as the resource. If the service doesn't exist, NGINX will assume the service has zero endpoints and return a ``502`` response for requests for this upstream. For NGINX Plus only, services of type [ExternalName](https://kubernetes.io/docs/concepts/services-networking/service/#externalname) are also supported (check the [prerequisites](https://github.com/nginx/kubernetes-ingress/tree/v{{< nic-version >}}/examples/ingress-resources/externalname-services#prerequisites) ). | ``string`` | Yes |
+|``service`` | The name of a [service](https://kubernetes.io/docs/concepts/services-networking/service/). If the Service belongs to a different namespace than the VirtualServer or VirtualServerRoute, you need to include the namespace. For example, ``tea-namespace/tea``. If the service doesn't exist, NGINX will assume the service has zero endpoints and return a ``502`` response for requests for this upstream. For NGINX Plus only, services of type [ExternalName](https://kubernetes.io/docs/concepts/services-networking/service/#externalname) are also supported in the same namespace (check the [prerequisites](https://github.com/nginx/kubernetes-ingress/tree/v{{< nic-version >}}/examples/ingress-resources/externalname-services#prerequisites) ). | ``string`` | Yes |
 |``subselector`` | Selects the pods within the service using label keys and values. By default, all pods of the service are selected. Note: the specified labels are expected to be present in the pods when they are created. If the pod labels are updated, NGINX Ingress Controller will not see that change until the number of the pods is changed. | ``map[string]string`` | No |
 |``use-cluster-ip`` | Enables using the Cluster IP and port of the service instead of the default behavior of using the IP and port of the pods. When this field is enabled, the fields that configure NGINX behavior related to multiple upstream servers (like ``lb-method`` and ``next-upstream``) will have no effect, as NGINX Ingress Controller will configure NGINX with only one upstream server that will match the service Cluster IP. | ``boolean`` | No |
 |``port`` | The port of the service. If the service doesn't define that port, NGINX will assume the service has zero endpoints and return a ``502`` response for requests for this upstream. The port must fall into the range ``1..65535``. | ``uint16`` | Yes |