dt-bindings: power: Clarify wording for wakeup-source property

The wording in the current documentation is a little strong. The
intention was not to fix any particular interrupt as wakeup capable but
leave those details to the device. It wasn't intended to enforce any
rules as what can be or can't be a wakeup interrupt.

Soften the wording to not mandate that the 'wakeup-source' property be
used, and clarify what it means when an interrupt is marked (or not
marked) for wakeup.

Link: https://lore.kernel.org/all/ZYAjxxHcCOgDVMTQ@bogus/
Link: https://lore.kernel.org/all/CAL_Jsq+MYwOG40X26cYmO9EkZ9xqWrXDi03MaRfxnV-+VGkXWQ@mail.gmail.com/Signed-off-by: Mark Hasemeyer <markhas@chromium.org>
Link: https://lore.kernel.org/r/20240102140734.v4.4.I1016a45ac9e8daf8a9ebc9854ab90ec3542e7c30@changeidSigned-off-by: Rob Herring <robh@kernel.org>

Documentation/devicetree/bindings/power/wakeup-source.txt

@@ -3,16 +3,20 @@ Specifying wakeup capability for devices
 
 Any device nodes
 ----------------
-Nodes that describe devices which has wakeup capability must contain an
+Nodes that describe devices which have wakeup capability may contain a
 "wakeup-source" boolean property.
 
-Also, if device is marked as a wakeup source, then all the primary
-interrupt(s) can be used as wakeup interrupt(s).
+If the device is marked as a wakeup-source, interrupt wake capability depends
+on the device specific "interrupt-names" property. If no interrupts are labeled
+as wake capable, then it is up to the device to determine which interrupts can
+wake the system.
 
-However if the devices have dedicated interrupt as the wakeup source
-then they need to specify/identify the same using device specific
-interrupt name. In such cases only that interrupt can be used as wakeup
-interrupt.
+However if a device has a dedicated interrupt as the wakeup source, then it
+needs to specify/identify it using a device specific interrupt name. In such
+cases only that interrupt can be used as a wakeup interrupt.
+
+While various legacy interrupt names exist, new devices should use "wakeup" as
+the canonical interrupt name.
 
 List of legacy properties and respective binding document
 ---------------------------------------------------------