ALSA: doc: ReSTize powersave document

A simple conversion from a text file.
Put into designs subdirectory, although it's mostly relevant with
HD-audio.
Signed-off-by: NTakashi Iwai <tiwai@suse.de>

Documentation/sound/designs/index.rst

@@ -5,3 +5,4 @@ Designs and Implementations
    :maxdepth: 2
 
    procfile
+   powersave

Documentation/sound/alsa/powersave.txt → Documentation/sound/designs/powersave.rst

+==========================
 Notes on Power-Saving Mode
 ==========================
 
 AC97 and HD-audio drivers have the automatic power-saving mode.
-This feature is enabled via Kconfig CONFIG_SND_AC97_POWER_SAVE
-and CONFIG_SND_HDA_POWER_SAVE options, respectively.
+This feature is enabled via Kconfig ``CONFIG_SND_AC97_POWER_SAVE``
+and ``CONFIG_SND_HDA_POWER_SAVE`` options, respectively.
 
 With the automatic power-saving, the driver turns off the codec power
 appropriately when no operation is required.  When no applications use
@@ -11,20 +12,21 @@ the device and/or no analog loopback is set, the power disablement is
 done fully or partially.  It'll save a certain power consumption, thus
 good for laptops (even for desktops).
 
-The time-out for automatic power-off can be specified via power_save
+The time-out for automatic power-off can be specified via ``power_save``
 module option of snd-ac97-codec and snd-hda-intel modules.  Specify
 the time-out value in seconds.  0 means to disable the automatic
 power-saving.  The default value of timeout is given via
-CONFIG_SND_AC97_POWER_SAVE_DEFAULT and
-CONFIG_SND_HDA_POWER_SAVE_DEFAULT Kconfig options.  Setting this to 1
+``CONFIG_SND_AC97_POWER_SAVE_DEFAULT`` and
+``CONFIG_SND_HDA_POWER_SAVE_DEFAULT`` Kconfig options.  Setting this to 1
 (the minimum value) isn't recommended because many applications try to
 reopen the device frequently.  10 would be a good choice for normal
 operations.
 
-The power_save option is exported as writable.  This means you can
+The ``power_save`` option is exported as writable.  This means you can
 adjust the value via sysfs on the fly.  For example, to turn on the
 automatic power-save mode with 10 seconds, write to
-/sys/modules/snd_ac97_codec/parameters/power_save (usually as root):
+``/sys/modules/snd_ac97_codec/parameters/power_save`` (usually as root):
+::
 
 	# echo 10 > /sys/modules/snd_ac97_codec/parameters/power_save