PM / core / docs: Convert sleep states API document to reST

Move the document describing the system sleep state transitions API
for devices to Documentation/driver-api/pm/, convert it to reST and
update it to use current terminology.  Also remove the remaining
reference to the old version of it from pm.h.

The new document still contains references to some documents in the
.txt format that will be converted later.
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

Documentation/driver-api/index.rst

@@ -16,6 +16,7 @@ available subsections can be seen below.
 
    basics
    infrastructure
+   pm/index
    device-io
    dma-buf
    device_link

Documentation/driver-api/pm/conf.py

+# -*- coding: utf-8; mode: python -*-
+
+project = "Device Power Management"
+
+tags.add("subproject")
+
+latex_documents = [
+    ('index', 'pm.tex', project,
+     'The kernel development community', 'manual'),
+]

Documentation/driver-api/pm/index.rst

+=======================
+Device Power Management
+=======================
+
+.. toctree::
+
+   devices
+   types
+
+.. only::  subproject and html
+
+   Indices
+   =======
+
+   * :ref:`genindex`

Documentation/driver-api/pm/types.rst

+==================================
+Device Power Management Data Types
+==================================
+
+.. kernel-doc:: include/linux/pm.h

include/linux/pm.h

@@ -276,9 +276,6 @@ typedef struct pm_message {
  * example, if it detects that a child was unplugged while the system was
  * asleep).
  *
- * Refer to Documentation/power/devices.txt for more information about the role
- * of the above callbacks in the system suspend process.
- *
  * There also are callbacks related to runtime power management of devices.
  * Again, as a rule these callbacks are executed by the PM core for subsystems
  * (PM domains, device types, classes and bus types) and the subsystem-level