Merge branch 'acpi-doc'

* acpi-doc:
  Documentation / CPU hotplug: Rephrase the outdated description for MADT entries
  ACPI / video: update video_extension.txt for backlight control
  ACPI / video: move video_extension.txt to Documentation/acpi
  ACPI / video: add description for brightness_switch_enabled
  ACPI: Add ACPI namespace documentation
  ACPI: Add sysfs ABI documentation
  ACPI: Update MAINTAINERS file to include Documentation/acpi