pm: device: Add wakeup source API

Introduce a new API to allow devices capable of wake up the system
register themselves was wake up sources. This permits applications to
select the most appropriate way to wake up the system when it is
suspended.

Signed-off-by: Flavio Ceolin <flavio.ceolin@intel.com>

dts/bindings/base/base.yaml

@@ -1,5 +1,7 @@
 # Common fields for all devices
 
+include: [pm.yaml]
+
 properties:
     status:
         type: string

dts/bindings/base/pm.yaml

@@ -0,0 +1,18 @@
+# Copyright (c) 2021 Intel Corporation.
+# SPDX-License-Identifier: Apache-2.0
+
+# Properties for Power Management (PM)
+
+properties:
+    wakeup-source:
+      required: false
+      type: boolean
+      description: |
+        Property to identify that a device can be used as wake up source.
+
+        When this property is provided a specific flag is set into the
+        device that tells the system that the device is capable of
+        wake up the system.
+
+        Wake up capable devices are disabled (interruptions will not wake up
+        the system) by default but they can be enabled at runtime if necessary.