drm/doc: Overview documentation for drm_mm.c

kerneldoc polish will follow in the next patch.

Hopefully documenting the lru scan support a bit better spurs someone
to give this a shot in the ttm eviction code. At least in i915 it
helped quite a lot with memory thrashing on platforms where eviction
was (we've fixed that too meanwhile) fairly expensive.

Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
diff --git a/Documentation/DocBook/drm.tmpl b/Documentation/DocBook/drm.tmpl
index dd2a955..2ac018b 100644
--- a/Documentation/DocBook/drm.tmpl
+++ b/Documentation/DocBook/drm.tmpl
@@ -920,6 +920,17 @@
 	<title>PRIME Function References</title>
 !Edrivers/gpu/drm/drm_prime.c
       </sect2>
+      <sect2>
+	<title>DRM MM Range Allocator</title>
+	<sect3>
+	  <title>Overview</title>
+!Pdrivers/gpu/drm/drm_mm.c Overview
+	</sect3>
+	<sect3>
+	  <title>LRU Scan/Eviction Support</title>
+!Pdrivers/gpu/drm/drm_mm.c lru scan roaster
+	</sect3>
+      </sect2>
   </sect1>
 
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