doc: contribute: DTS style guideline updates

This is a follow-up from a recent debate on Discord about whether
splitting up related groups of properties is OK. Record the consensus
outcome of the debate so this question is easier to answer next time.

Signed-off-by: Martí Bolívar <marti.bolivar@oss.qualcomm.com>

Author: mbolivar

doc/contribute/style/devicetree.rst

@@ -5,6 +5,12 @@ Devicetree Style Guidelines
 
   * Indent with tabs.
   * Follow the Devicetree specification conventions and rules.
+  * If the Linux kernel rules in
+    `Devicetree Sources (DTS) Coding Style <https://docs.kernel.org/devicetree/bindings/dts-coding-style.html>`_
+    make a recommendation, it's the preferred style in Zephyr too.
+  * You can split related groups of properties into "paragraphs" by
+    separating them with one empty line (two newline characters) if it aids
+    readability.
   * Use dashes (``-``) as word separators for node and property names.
   * Use underscores (``_``) as word separators in node labels.
   * Leave a single space on each side of the equal sign (``=``) in property