Merge pull request #267 from kube-logging/syslog-ng-filter-metadata-c…

…larifications

Minor clarifications about syslog-ng label filtering

content/docs/configuration/log-routing-syslog-ng.md

@@ -95,7 +95,7 @@ Defines the pattern to match against the messages. The [`type` field](#regexp-ty
 
 ### `value` (string) {#regexp-value class="property-optional"}
 
-References a field of the message. The `pattern` is applied to the value of this field. If the `value` field is set, you cannot use the `template` field.
+References a field of the message. The `pattern` is applied to the value of this field. If the `value` field is set, you cannot use the `template` field. When matching for labels or annotations, the available labels and annotations depend on the incoming message received from the log collector agent. See this [list of common Kubernetes labels and annotations](https://kubernetes.io/docs/reference/labels-annotations-taints/) for details.
 
 {{< include-headless "field-names-json-prefix.md" >}}
 

content/docs/configuration/plugins/syslog-ng-filters/match.md

@@ -4,7 +4,7 @@ weight: 200
 generated_file: true
 ---
 
-Match filters can be used to select the log records to process. These filters have the same options and syntax as [syslog-ng flow match expressions]({{< relref "/docs/configuration/plugins/syslog-ng-filters/match.md" >}}).
+Match filters can be used to select the log records to process. These filters have the same options and syntax as [syslog-ng flow match expressions]({{< relref "/docs/configuration/log-routing-syslog-ng.md" >}}). When matching for labels or annotations, the available labels and annotations depend on the incoming message received from the log collector agent. See this [list of common Kubernetes labels and annotations](https://kubernetes.io/docs/reference/labels-annotations-taints/) for details.
 
 {{< highlight yaml >}}
 filters: