hwmon/coretemp: Add documentation

Documentation for the coretemp driver.

Signed-off-by: Rudolf Marek <r.marek@assembler.cz>
Signed-off-by: Jean Delvare <khali@linux-fr.org>

diff --git a/Documentation/hwmon/coretemp b/Documentation/hwmon/coretemp
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+Kernel driver coretemp
+======================
+
+Supported chips:
+  * All Intel Core family
+    Prefix: 'coretemp'
+    CPUID: family 0x6, models 0xe, 0xf
+    Datasheet: Intel 64 and IA-32 Architectures Software Developer's Manual
+               Volume 3A: System Programming Guide
+
+Author: Rudolf Marek
+
+Description
+-----------
+
+This driver permits reading temperature sensor embedded inside Intel Core CPU.
+Temperature is measured in degrees Celsius and measurement resolution is
+1 degree C. Valid temperatures are from 0 to TjMax degrees C, because
+the actual value of temperature register is in fact a delta from TjMax.
+
+Temperature known as TjMax is the maximum junction temperature of processor.
+Intel defines this temperature as 85C or 100C. At this temperature, protection
+mechanism will perform actions to forcibly cool down the processor. Alarm
+may be raised, if the temperature grows enough (more than TjMax) to trigger
+the Out-Of-Spec bit. Following table summarizes the exported sysfs files:
+
+temp1_input     - Core temperature (in millidegrees Celsius).
+temp1_crit      - Maximum junction temperature  (in millidegrees Celsius).
+temp1_crit_alarm - Set when Out-of-spec bit is set, never clears.
+                  Correct CPU operation is no longer guaranteed.
+temp1_label     - Contains string "Core X", where X is processor
+                  number.
+
+The TjMax temperature is set to 85 degrees C if undocumented model specific
+register (UMSR) 0xee has bit 30 set. If not the TjMax is 100 degrees C as
+(sometimes) documented in processor datasheet.