docs: dt: convert changesets to ReST

- Add a SPDX header;
- Add a document title;
- Some whitespace fixes and new line breaks;
- Add it to devicetree/index.rst.
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Signed-off-by: Rob Herring <robh@kernel.org>

Documentation/devicetree/changesets.txt → Documentation/devicetree/changesets.rst

+.. SPDX-License-Identifier: GPL-2.0
+
+=============
+DT Changesets
+=============
+
 A DT changeset is a method which allows one to apply changes
 in the live tree in such a way that either the full set of changes
 will be applied, or none of them will be. If an error occurs partway
@@ -15,17 +21,17 @@ The sequence of a changeset is as follows.
 1. of_changeset_init() - initializes a changeset
 
 2. A number of DT tree change calls, of_changeset_attach_node(),
-of_changeset_detach_node(), of_changeset_add_property(),
-of_changeset_remove_property, of_changeset_update_property() to prepare
-a set of changes. No changes to the active tree are made at this point.
-All the change operations are recorded in the of_changeset 'entries'
-list.
+   of_changeset_detach_node(), of_changeset_add_property(),
+   of_changeset_remove_property, of_changeset_update_property() to prepare
+   a set of changes. No changes to the active tree are made at this point.
+   All the change operations are recorded in the of_changeset 'entries'
+   list.
 
 3. of_changeset_apply() - Apply the changes to the tree. Either the
-entire changeset will get applied, or if there is an error the tree will
-be restored to the previous state. The core ensures proper serialization
-through locking. An unlocked version __of_changeset_apply is available,
-if needed.
+   entire changeset will get applied, or if there is an error the tree will
+   be restored to the previous state. The core ensures proper serialization
+   through locking. An unlocked version __of_changeset_apply is available,
+   if needed.
 
 If a successfully applied changeset needs to be removed, it can be done
 with of_changeset_revert().

Documentation/devicetree/index.rst

@@ -9,3 +9,4 @@ Open Firmware and Device Tree
 
    usage-model
    writing-schema
+   changesets