doc: dts: clarify reg format
These are in hex.
Suggested-by: Jamie McCrae
@@ -253,7 +253,10 @@ reg
(i.e. is different depending on the compatible property).
The ``reg`` property is a sequence of ``(address, length)`` pairs. Each
- pair is called a "register block". Here are some common patterns:
+ pair is called a "register block". Values are conventionally written
+ in hex.
+
+ Here are some common patterns:
- Devices accessed via memory-mapped I/O registers (like ``i2c@40003000``):
``address`` is usually the base address of the I/O register space, and
