drm/i915: Kerneldoc for intel_runtime_pm.c

I've decided not to document the functions exported to the audio
driver since really, they shouldn't exist ...

v2: Improvements from Imre's review plus a few more spelling fixes
I've spotted.
Reviewed-by: Imre Deak <imre.deak@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

Documentation/DocBook/drm.tmpl

@@ -3787,6 +3787,18 @@ int num_ioctls;</synopsis>
       blocks. This excludes a set of SoC platforms with an SGX rendering unit,
       those have basic support through the gma500 drm driver.
     </para>
+    <sect1>
+      <title>Core Driver Infrastructure</title>
+      <para>
+	This section covers core driver infrastructure used by both the display
+	and the GEM parts of the driver.
+      </para>
+      <sect2>
+        <title>Runtime Power Management</title>
+!Pdrivers/gpu/drm/i915/intel_runtime_pm.c runtime pm
+!Idrivers/gpu/drm/i915/intel_runtime_pm.c
+      </sect2>
+    </sect1>
     <sect1>
       <title>Display Hardware Handling</title>
       <para>