docs: dt: submitting-patches: Fix grammar in subsystem section

Reword the subsystem bindings section to make sense, from a grammatical
point of view.
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Acked-by: Randy Dunlap <rdunlap@infradead.org>
Link: https://lore.kernel.org/r/20210309130650.2318419-1-geert+renesas@glider.beSigned-off-by: Jonathan Corbet <corbet@lwn.net>

Documentation/devicetree/bindings/submitting-patches.rst

@@ -75,8 +75,8 @@ II. For kernel maintainers
      binding, and it hasn't received an Acked-by from the devicetree
      maintainers after a few weeks, go ahead and take it.
 
-     Subsystem bindings (anything affecting more than a single device)
-     then getting a devicetree maintainer to review it is required.
+     For subsystem bindings (anything affecting more than a single device),
+     getting a devicetree maintainer to review it is required.
 
   3) For a series going though multiple trees, the binding patch should be
      kept with the driver using the binding.