[Feature]add MT2731_MP2_MR2_SVN388 baseline version
Change-Id: Ief04314834b31e27effab435d3ca8ba33b499059
diff --git a/src/kernel/linux/v4.14/Documentation/devicetree/overlay-notes.txt b/src/kernel/linux/v4.14/Documentation/devicetree/overlay-notes.txt
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+Device Tree Overlay Notes
+-------------------------
+
+This document describes the implementation of the in-kernel
+device tree overlay functionality residing in drivers/of/overlay.c and is a
+companion document to Documentation/devicetree/dynamic-resolution-notes.txt[1]
+
+How overlays work
+-----------------
+
+A Device Tree's overlay purpose is to modify the kernel's live tree, and
+have the modification affecting the state of the kernel in a way that
+is reflecting the changes.
+Since the kernel mainly deals with devices, any new device node that result
+in an active device should have it created while if the device node is either
+disabled or removed all together, the affected device should be deregistered.
+
+Lets take an example where we have a foo board with the following base tree:
+
+---- foo.dts -----------------------------------------------------------------
+ /* FOO platform */
+ / {
+ compatible = "corp,foo";
+
+ /* shared resources */
+ res: res {
+ };
+
+ /* On chip peripherals */
+ ocp: ocp {
+ /* peripherals that are always instantiated */
+ peripheral1 { ... };
+ }
+ };
+---- foo.dts -----------------------------------------------------------------
+
+The overlay bar.dts, when loaded (and resolved as described in [1]) should
+
+---- bar.dts -----------------------------------------------------------------
+/plugin/; /* allow undefined label references and record them */
+/ {
+ .... /* various properties for loader use; i.e. part id etc. */
+ fragment@0 {
+ target = <&ocp>;
+ __overlay__ {
+ /* bar peripheral */
+ bar {
+ compatible = "corp,bar";
+ ... /* various properties and child nodes */
+ }
+ };
+ };
+};
+---- bar.dts -----------------------------------------------------------------
+
+result in foo+bar.dts
+
+---- foo+bar.dts -------------------------------------------------------------
+ /* FOO platform + bar peripheral */
+ / {
+ compatible = "corp,foo";
+
+ /* shared resources */
+ res: res {
+ };
+
+ /* On chip peripherals */
+ ocp: ocp {
+ /* peripherals that are always instantiated */
+ peripheral1 { ... };
+
+ /* bar peripheral */
+ bar {
+ compatible = "corp,bar";
+ ... /* various properties and child nodes */
+ }
+ }
+ };
+---- foo+bar.dts -------------------------------------------------------------
+
+As a result of the overlay, a new device node (bar) has been created
+so a bar platform device will be registered and if a matching device driver
+is loaded the device will be created as expected.
+
+Overlay in-kernel API
+--------------------------------
+
+The API is quite easy to use.
+
+1. Call of_overlay_create() to create and apply an overlay. The return value
+is a cookie identifying this overlay.
+
+2. Call of_overlay_destroy() to remove and cleanup the overlay previously
+created via the call to of_overlay_create(). Removal of an overlay that
+is stacked by another will not be permitted.
+
+Finally, if you need to remove all overlays in one-go, just call
+of_overlay_destroy_all() which will remove every single one in the correct
+order.
+
+Overlay DTS Format
+------------------
+
+The DTS of an overlay should have the following format:
+
+{
+ /* ignored properties by the overlay */
+
+ fragment@0 { /* first child node */
+
+ target=<phandle>; /* phandle target of the overlay */
+ or
+ target-path="/path"; /* target path of the overlay */
+
+ __overlay__ {
+ property-a; /* add property-a to the target */
+ node-a { /* add to an existing, or create a node-a */
+ ...
+ };
+ };
+ }
+ fragment@1 { /* second child node */
+ ...
+ };
+ /* more fragments follow */
+}
+
+Using the non-phandle based target method allows one to use a base DT which does
+not contain a __symbols__ node, i.e. it was not compiled with the -@ option.
+The __symbols__ node is only required for the target=<phandle> method, since it
+contains the information required to map from a phandle to a tree location.