trivial: update 0.13.0 release note info on linux arm builds

Author: mruddy

doc/release-notes/release-notes-0.13.0.md

@@ -95,14 +95,19 @@ executables.
 
 The following extra files can be found in the download directory or torrent:
 
-- `bitcoin-${VERSION}-arm-linux-gnueabihf.tar.gz`: Linux binaries for the most
-  common 32-bit ARM architecture.
-- `bitcoin-${VERSION}-aarch64-linux-gnu.tar.gz`: Linux binaries for the most
-  common 64-bit ARM architecture.
+- `bitcoin-${VERSION}-arm-linux-gnueabihf.tar.gz`: Linux binaries targeting
+  the 32-bit ARMv7-A architecture.
+- `bitcoin-${VERSION}-aarch64-linux-gnu.tar.gz`: Linux binaries targeting
+  the 64-bit ARMv8-A architecture.
 
 ARM builds are still experimental. If you have problems on a certain device or
 Linux distribution combination please report them on the bug tracker, it may be
-possible to resolve them.
+possible to resolve them. Note that the device you use must be (backward)
+compatible with the architecture targeted by the binary that you use.
+For example, a Raspberry Pi 2 Model B or Raspberry Pi 3 Model B (in its 32-bit
+execution state) device, can run the 32-bit ARMv7-A targeted binary. However,
+no model of Raspberry Pi 1 device can run either binary because they are all
+ARMv6 architecture devices that are not compatible with ARMv7-A or ARMv8-A.
 
 Note that Android is not considered ARM Linux in this context. The executables
 are not expected to work out of the box on Android.