diff --git a/drivers/gpu/drm/i915/i915_gem_object.h b/drivers/gpu/drm/i915/i915_gem_object.h
index 35e1a27729dc..915057824284 100644
--- a/drivers/gpu/drm/i915/i915_gem_object.h
+++ b/drivers/gpu/drm/i915/i915_gem_object.h
@@ -68,8 +68,23 @@ struct drm_i915_gem_object {
 
 	const struct drm_i915_gem_object_ops *ops;
 
-	/** List of VMAs backed by this object */
+	/**
+	 * @vma_list: List of VMAs backed by this object
+	 *
+	 * The VMA on this list are ordered by type, all GGTT vma are placed
+	 * at the head and all ppGTT vma are placed at the tail. The different
+	 * types of GGTT vma are unordered between themselves, use the
+	 * @vma_tree (which has a defined order between all VMA) to find an
+	 * exact match.
+	 */
 	struct list_head vma_list;
+	/**
+	 * @vma_tree: Ordered tree of VMAs backed by this object
+	 *
+	 * All VMA created for this object are placed in the @vma_tree for
+	 * fast retrieval via a binary search in i915_vma_instance().
+	 * They are also added to @vma_list for easy iteration.
+	 */
 	struct rb_root vma_tree;
 
 	/** Stolen memory for this object, instead of being backed by shmem. */