Documentation: ACPI: move dsd/data-node-references.txt to firmware-guide/acpi and convert to reST

This converts the plain text documentation to reStructuredText format
and adds it to Sphinx TOC tree.

No essential content change.

Signed-off-by: Changbin Du <changbin.du@gmail.com>
Reviewed-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

2 files changed, 94 insertions, 0 deletions

diff --git a/Documentation/firmware-guide/acpi/dsd/data-node-references.rst b/Documentation/firmware-guide/acpi/dsd/data-node-references.rst
new file mode 100644
index 000000000000..1351984e767c
--- /dev/null
+++ b/Documentation/firmware-guide/acpi/dsd/data-node-references.rst
@@ -0,0 +1,93 @@
+.. SPDX-License-Identifier: GPL-2.0
+.. include:: <isonum.txt>
+
+===================================
+Referencing hierarchical data nodes
+===================================
+
+:Copyright: |copy| 2018 Intel Corporation
+:Author: Sakari Ailus <sakari.ailus@linux.intel.com>
+
+ACPI in general allows referring to device objects in the tree only.
+Hierarchical data extension nodes may not be referred to directly, hence this
+document defines a scheme to implement such references.
+
+A reference consist of the device object name followed by one or more
+hierarchical data extension [1] keys. Specifically, the hierarchical data
+extension node which is referred to by the key shall lie directly under the
+parent object i.e. either the device object or another hierarchical data
+extension node.
+
+The keys in the hierarchical data nodes shall consist of the name of the node,
+"@" character and the number of the node in hexadecimal notation (without pre-
+or postfixes). The same ACPI object shall include the _DSD property extension
+with a property "reg" that shall have the same numerical value as the number of
+the node.
+
+In case a hierarchical data extensions node has no numerical value, then the
+"reg" property shall be omitted from the ACPI object's _DSD properties and the
+"@" character and the number shall be omitted from the hierarchical data
+extension key.
+
+
+Example
+=======
+
+In the ASL snippet below, the "reference" _DSD property [2] contains a
+device object reference to DEV0 and under that device object, a
+hierarchical data extension key "node@1" referring to the NOD1 object
+and lastly, a hierarchical data extension key "anothernode" referring to
+the ANOD object which is also the final target node of the reference.
+::
+
+        Device (DEV0)
+        {
+            Name (_DSD, Package () {
+                ToUUID("dbb8e3e6-5886-4ba6-8795-1319f52a966b"),
+                Package () {
+                    Package () { "node@0", NOD0 },
+                    Package () { "node@1", NOD1 },
+                }
+            })
+            Name (NOD0, Package() {
+                ToUUID("daffd814-6eba-4d8c-8a91-bc9bbf4aa301"),
+                Package () {
+                    Package () { "random-property", 3 },
+                }
+            })
+            Name (NOD1, Package() {
+                ToUUID("dbb8e3e6-5886-4ba6-8795-1319f52a966b"),
+                Package () {
+                    Package () { "anothernode", ANOD },
+                }
+            })
+            Name (ANOD, Package() {
+                ToUUID("daffd814-6eba-4d8c-8a91-bc9bbf4aa301"),
+                Package () {
+                    Package () { "random-property", 0 },
+                }
+            })
+        }
+
+        Device (DEV1)
+        {
+            Name (_DSD, Package () {
+                ToUUID("daffd814-6eba-4d8c-8a91-bc9bbf4aa301"),
+                Package () {
+                    Package () { "reference", ^DEV0, "node@1", "anothernode" },
+                }
+            })
+        }
+
+Please also see a graph example in :doc:`graph`.
+
+References
+==========
+
+[1] Hierarchical Data Extension UUID For _DSD.
+<http://www.uefi.org/sites/default/files/resources/_DSD-hierarchical-data-extension-UUID-v1.1.pdf>,
+referenced 2018-07-17.
+
+[2] Device Properties UUID For _DSD.
+<http://www.uefi.org/sites/default/files/resources/_DSD-device-properties-UUID.pdf>,
+referenced 2016-10-04.
diff --git a/Documentation/firmware-guide/acpi/index.rst b/Documentation/firmware-guide/acpi/index.rst
index f81cfbcb6878..6d4e0df4f063 100644
--- a/Documentation/firmware-guide/acpi/index.rst
+++ b/Documentation/firmware-guide/acpi/index.rst
@@ -9,6 +9,7 @@ ACPI Support
 
    namespace
    dsd/graph
+   dsd/data-node-references
    enumeration
    osi
    method-customizing