ACPI: ibm-acpi: document thermal sensor locations for the A31

The A31 has a very atypical layout, so I separated its thermal sensors
location in a separate patch.

Signed-off-by: Henrique de Moraes Holschuh <hmh@hmh.eng.br>
diff --git a/Documentation/ibm-acpi.txt b/Documentation/ibm-acpi.txt
index 30f09e7..333b8eb 100644
--- a/Documentation/ibm-acpi.txt
+++ b/Documentation/ibm-acpi.txt
@@ -448,6 +448,17 @@
 10: ICH (southbridge), under Mini-PCI card, under touchpad
 11: Power regulator, underside of system board, below F2 key
 
+The A31 has a very atypical layout for the thermal sensors
+(source: Milos Popovic, http://thinkwiki.org/wiki/Thermal_Sensors#ThinkPad_A31)
+1:  CPU
+2:  Main Battery: main sensor
+3:  Power Converter
+4:  Bay Battery: main sensor
+5:  MCH (northbridge)
+6:  PCMCIA/ambient
+7:  Main Battery: secondary sensor
+8:  Bay Battery: secondary sensor
+
 
 EXPERIMENTAL: Embedded controller register dump -- /proc/acpi/ibm/ecdump
 ------------------------------------------------------------------------