Add output class document

Patch 4/5: add output class document

---
 video-output.txt |   34 ++++++++++++++++++++++++++++++++++
 1 file changed, 34 insertions(+)

new file mode 100644
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+
+		Video Output Switcher Control
+		~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+		2006 [email protected]
+
+The output sysfs class driver provides an abstract video output layer that 
+can be used to hook platform specific methods to enable/disable video output
+device through common sysfs interface. For example, on my IBM ThinkPad T42 
+laptop, The ACPI video driver registered its output devices and read/write 
+method for 'state' with output sysfs class. The user interface under sysfs 

is:
+
+linux:/sys/class/video_output # tree .
+.

+|-- CRT0
+|   |-- device -> ../../../devices/pci0000:00/0000:00:01.0
+|   |-- state
+|   |-- subsystem -> ../../../class/video_output
+|   `-- uevent
+|-- DVI0
+|   |-- device -> ../../../devices/pci0000:00/0000:00:01.0
+|   |-- state
+|   |-- subsystem -> ../../../class/video_output
+|   `-- uevent
+|-- LCD0
+|   |-- device -> ../../../devices/pci0000:00/0000:00:01.0
+|   |-- state
+|   |-- subsystem -> ../../../class/video_output
+|   `-- uevent
+`-- TV0
+   |-- device -> ../../../devices/pci0000:00/0000:00:01.0
+   |-- state
+   |-- subsystem -> ../../../class/video_output
+   `-- uevent

+