dt-bindings: remoteproc: pru: Update bindings for K3 AM65x SoCs

The K3 AM65x SoCs have the next generation of the PRU-ICSS IP, commonly
called ICSSG. The ICSSG IP on K3 SoCs has two PRU cores and two additional
custom PRU cores called Real Time Units (RTUs). Update the PRU binings
for these newer generarion ICSSG instances.

Signed-off-by: Suman Anna <s-anna@ti.com>

Documentation/devicetree/bindings/remoteproc/ti,pru-rproc.txt

@@ -1,13 +1,16 @@
-PRU Core on TI SoCs
-===================
+PRU/RTU Core on TI SoCs
+=======================
 
 Each PRUSS has dual PRU cores, each represented by a PRU node. Each PRU core
 has a dedicated Instruction RAM, Control and Debug register sets, and use
-the Data RAMs present within the PRUSS for code execution.
+the Data RAMs present within the PRUSS for code execution. K3 SoCs have two
+additional PRU cores called RTUs with slightly different IP integration. Each
+RTU core can be used independently like a PRU, or alongside a corresponding
+PRU core to provide/implement auxiliary functionality/support.
 
-Each PRU core node should be defined as a child node of the corresponding PRUSS
-node. Each node can optionally be rendered inactive by using the standard DT
-string property, "status".
+Each PRU or RTU core node should be defined as a child node of the corresponding
+PRUSS node. Each node can optionally be rendered inactive by using the standard
+DT string property, "status".
 
 Please see the overall PRUSS bindings document for additional details
 including a complete example,
@@ -20,6 +23,8 @@ Required Properties:
                        "ti,am4376-pru" for AM437x family of SoCs
                        "ti,am5728-pru" for AM57xx family of SoCs
                        "ti,k2g-pru" for 66AK2G family of SoCs
+                       "ti,am654-pru" for PRUs in K3 AM65x family of SoCs
+                       "ti,am654-rtu" for RTUs in K3 AM65x family of SoCs
 - reg            : base address and size for each of the 3 sub-module address
                    spaces as mentioned in reg-names, and in the same order as
                    the reg-names
@@ -72,7 +77,7 @@ devices, so below are in addition to each node's bindings.
 
 Required Properties:
 --------------------
-- prus                 : phandles to the PRU nodes used
+- prus                 : phandles to the PRU or RTU nodes used
 
 Optional Properties:
 --------------------