doc/sensors: be explicit about the encoding of sensor ID/handle not being ABI

Signed-off-by: Stewart Smith <stewart@linux.vnet.ibm.com>

Author: stewartsmith

doc/device-tree/ibm,opal/sensors.rst

@@ -22,7 +22,8 @@ Each node has a minimum set of properties describing the sensor :
 
 - a "sensor-data" property giving a unique handler for the
   OPAL_SENSOR_READ call to be used by Linux to get the value of
-  a sensor attribute. A sensor handler has the following encoding : ::
+  a sensor attribute. This value is opaque to the OS but is *currently*
+  constructed using the following encoding : ::
 
 		|  Attr. |Fam|Res. |   Resource     |
 		| Number |ily|Class|      Id        |

doc/opal-api/opal-sensor-read-88.rst

@@ -2,8 +2,9 @@ OPAL_SENSOR_READ
 ================
 
 The OPAL sensor call reads a sensor data using a unique handler to
-identity the targeted sensor.
-
+identity the targeted sensor. The `sensor_handler` is provided
+via the device tree and is opaque to the OS (although we currently
+do use an encoding scheme).
 
 This call can be asynchronous, when a message needs to be sent to a
 service processor for example.  In this case, the call will return