dt-binding: memory: pl353-smc: Rephrase the binding

Reword this document before converting it to yaml.
Signed-off-by: NMiquel Raynal <miquel.raynal@bootlin.com>
Acked-by: NRob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20210610082040.2075611-2-miquel.raynal@bootlin.comSigned-off-by: NKrzysztof Kozlowski <krzysztof.kozlowski@canonical.com>

Documentation/devicetree/bindings/memory-controllers/pl353-smc.txt

 Device tree bindings for ARM PL353 static memory controller
 
-PL353 static memory controller supports two kinds of memory
-interfaces.i.e NAND and SRAM/NOR interfaces.
-The actual devices are instantiated from the child nodes of pl353 smc node.
+PL353 Static Memory Controller is a bus where you can connect two kinds
+of memory interfaces: NAND and memory mapped interfaces (such as SRAM or NOR).
 
 Required properties:
 - compatible		: Should be "arm,pl353-smc-r2p1", "arm,primecell".
@@ -13,9 +12,9 @@ Required properties:
 - address-cells		: Must be 2.
 - size-cells		: Must be 1.
 
-Child nodes:
- For NAND the "arm,pl353-nand-r2p1" and for NOR the "cfi-flash" drivers are
-supported as child nodes.
+The child device node represents the controller connected to the SMC
+bus. Only one between: NAND controller, NOR controller and SRAM controller
+is allowed in a single system.
 
 for NAND partition information please refer the below file
 Documentation/devicetree/bindings/mtd/partition.txt