Documentation: alienware-wmi: Describe THERMAL_INFORMATION operation 0x02

This operation is used by alienware-wmi driver to avoid brute-forcing
operation 0x03.

Signed-off-by: Kurt Borja <kuurtb@gmail.com>
Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Link: https://lore.kernel.org/r/20241111183639.14726-1-kuurtb@gmail.com
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>

Author: kuu-rt

Documentation/wmi/devices/alienware-wmi.rst

@@ -96,7 +96,7 @@ WMI method Thermal_Information([in] uint32 arg2, [out] uint32 argr)
          argr = 1
 
  if BYTE_0(arg2) == 0x02:
-         argr = UNKNOWN_CONSTANT
+         argr = SYSTEM_DESCRIPTION
 
  if BYTE_0(arg2) == 0x03:
          if BYTE_1(arg2) == 0x00:
@@ -179,6 +179,16 @@ WMI method Thermal_Information([in] uint32 arg2, [out] uint32 argr)
          else:
                  argr = 0xFFFFFFFF
 
+Operation 0x02 returns a *system description* buffer with the following
+structure:
+
+::
+
+ out[0] -> Number of fans
+ out[1] -> Number of sensors
+ out[2] -> 0x00
+ out[3] -> Number of thermal modes
+
 Operation 0x03 list all available fan IDs, sensor IDs and thermal profile
 codes in order, but different models may have different number of fans and
 thermal profiles. These are the known ranges: