Item: Add description for associations involving Bmc

Change-Id: I9aa0fe58c5ab0c47f168c1340fd8c328ad7f6e9e
Signed-off-by: Sui Chen <suichen@google.com>
diff --git a/yaml/xyz/openbmc_project/Sensor/Value.interface.yaml b/yaml/xyz/openbmc_project/Sensor/Value.interface.yaml
index 77cef58..dd80468 100644
--- a/yaml/xyz/openbmc_project/Sensor/Value.interface.yaml
+++ b/yaml/xyz/openbmc_project/Sensor/Value.interface.yaml
@@ -99,4 +99,12 @@
       reverse_names:
           - sensors
       required_endpoint_interfaces:
-          - xyz.openbmc_project.Inventory.Item
\ No newline at end of file
+          - xyz.openbmc_project.Inventory.Item
+    - name: monitoring
+      description: >
+          Sensors may monitor the BMC's resource utilization and implement
+          an associatoin to the Bmc item.
+      reverse_names:
+          - monitored_by
+      required_endpoint_interfaces:
+          - xyz.openbmc_project.Inventory.Item.Bmc