Clarify difference between surface material and surface override material

(cherry picked from commit f4fd6d0d99938c55ea22282f5a189f0e67ab0163)

doc/classes/Mesh.xml

@@ -162,14 +162,14 @@
 		<method name="get_surface_count" qualifiers="const">
 			<return type="int" />
 			<description>
-				Returns the number of surfaces that the [Mesh] holds.
+				Returns the number of surfaces that the [Mesh] holds. This is equivalent to [method MeshInstance3D.get_surface_override_material_count].
 			</description>
 		</method>
 		<method name="surface_get_arrays" qualifiers="const">
 			<return type="Array" />
 			<param index="0" name="surf_idx" type="int" />
 			<description>
-				Returns the arrays for the vertices, normals, uvs, etc. that make up the requested surface (see [method ArrayMesh.add_surface_from_arrays]).
+				Returns the arrays for the vertices, normals, UVs, etc. that make up the requested surface (see [method ArrayMesh.add_surface_from_arrays]).
 			</description>
 		</method>
 		<method name="surface_get_blend_shape_arrays" qualifiers="const">
@@ -184,6 +184,7 @@
 			<param index="0" name="surf_idx" type="int" />
 			<description>
 				Returns a [Material] in a given surface. Surface is rendered using this material.
+				[b]Note:[/b] This returns the material within the [Mesh] resource, not the [Material] associated to the [MeshInstance3D]'s Surface Material Override properties. To get the [Material] associated to the [MeshInstance3D]'s Surface Material Override properties, use [method MeshInstance3D.get_surface_override_material] instead.
 			</description>
 		</method>
 		<method name="surface_set_material">
@@ -192,6 +193,7 @@
 			<param index="1" name="material" type="Material" />
 			<description>
 				Sets a [Material] for a given surface. Surface will be rendered using this material.
+				[b]Note:[/b] This assigns the material within the [Mesh] resource, not the [Material] associated to the [MeshInstance3D]'s Surface Material Override properties. To set the [Material] associated to the [MeshInstance3D]'s Surface Material Override properties, use [method MeshInstance3D.set_surface_override_material] instead.
 			</description>
 		</method>
 	</methods>

doc/classes/MeshInstance3D.xml

@@ -74,13 +74,14 @@
 			<return type="Material" />
 			<param index="0" name="surface" type="int" />
 			<description>
-				Returns the override [Material] for the specified [param surface] of the [Mesh] resource.
+				Returns the override [Material] for the specified [param surface] of the [Mesh] resource. See also [method get_surface_override_material_count].
+				[b]Note:[/b] This returns the [Material] associated to the [MeshInstance3D]'s Surface Material Override properties, not the material within the [Mesh] resource. To get the material within the [Mesh] resource, use [method Mesh.surface_get_material] instead.
 			</description>
 		</method>
 		<method name="get_surface_override_material_count" qualifiers="const">
 			<return type="int" />
 			<description>
-				Returns the number of surface override materials. This is equivalent to [method Mesh.get_surface_count].
+				Returns the number of surface override materials. This is equivalent to [method Mesh.get_surface_count]. See also [method get_surface_override_material].
 			</description>
 		</method>
 		<method name="set_blend_shape_value">
@@ -97,6 +98,7 @@
 			<param index="1" name="material" type="Material" />
 			<description>
 				Sets the override [param material] for the specified [param surface] of the [Mesh] resource. This material is associated with this [MeshInstance3D] rather than with [member mesh].
+				[b]Note:[/b] This assigns the [Material] associated to the [MeshInstance3D]'s Surface Material Override properties, not the material within the [Mesh] resource. To set the material within the [Mesh] resource, use [method Mesh.surface_get_material] instead.
 			</description>
 		</method>
 	</methods>