diff --git a/scripts/dts/gen_defines.py b/scripts/dts/gen_defines.py
index a302d538364..2cd590e5da1 100755
--- a/scripts/dts/gen_defines.py
+++ b/scripts/dts/gen_defines.py
@@ -1,6 +1,6 @@
 #!/usr/bin/env python3
 
-# Copyright (c) 2019 Nordic Semiconductor ASA
+# Copyright (c) 2019 - 2020 Nordic Semiconductor ASA
 # Copyright (c) 2019 Linaro Limited
 # SPDX-License-Identifier: BSD-3-Clause
 
@@ -278,25 +278,74 @@ def relativize(path):
 
 
 def write_regs(node):
-    # Writes address/size output for the registers in the node's 'reg' property
+    # Writes address/size output for the registers in the node's 'reg'
+    # property. This is where the BASE_ADDRESS and SIZE macros come from.
 
-    def write_reg(reg, base_ident, val):
-        # Drop '_0' from the identifier if there's a single register, for
-        # backwards compatibility
-        if len(reg.node.regs) > 1:
-            ident = f"{base_ident}_{reg.node.regs.index(reg)}"
+    if not node.regs:
+        return
+
+    # This maps a reg_i (see below) to the "primary" BASE_ADDRESS and SIZE
+    # macros used to identify it, which look like:
+    #
+    #   DT_<PRIMARY_NODE_IDENTIFIER>_BASE_ADDRESS_<reg_i>
+    #   DT_<PRIMARY_NODE_IDENTIFIER>_SIZE_<reg_i>
+    #
+    # Or, for backwards compatibility if there's only one reg:
+    #
+    #   DT_<IDENT>_BASE_ADDRESS
+    #   DT_<IDENT>_SIZE
+    #
+    # It's up to augment_node() to decide which identifier for the
+    # node is its "primary" identifier, and which identifiers are
+    # "other" identifiers. The "other" identifier BASE_ADDRESS and
+    # SIZE macros are defined in terms of the "primary" ones.
+    reg_i2primary_addr_size = {}
+
+    def write_regs_for_ident(node, ident):
+        # Write BASE_ADDRESS and SIZE macros for a given identifier
+        # 'ident'. If we have already generated primary address and
+        # size macros and saved in them in primary_addrs and
+        # primary_sizes, we just reuse those. Otherwise (i.e. the
+        # first time this is called), they are generated from the
+        # actual reg.addr and reg.size attributes, and the names of
+        # the primary macros are saved.
+
+        for reg_i, reg in enumerate(node.regs):
+            # DT_<IDENT>_BASE_ADDRESS_<reg_i>
+            # DT_<IDENT>_SIZE_<reg_i>
+            prim_addr, prim_size = reg_i2primary_addr_size.get(reg_i,
+                                                               (None, None))
+            suffix = f"_{reg_i}" if len(node.regs) > 1 else ""
+
+            if prim_addr is not None:
+                write_reg(ident, reg, prim_addr, prim_size,
+                          "", suffix)
+            else:
+                prim_addr, prim_size = write_reg(ident, reg, None, None,
+                                                 "", suffix)
+                reg_i2primary_addr_size[reg_i] = (prim_addr, prim_size)
+
+            # DT_<IDENT>_<reg.name>_BASE_ADDRESS
+            # DT_<IDENT>_<reg.name>_SIZE
+            if reg.name:
+                write_reg(ident, reg, prim_addr, prim_size,
+                          f"{str2ident(reg.name)}_", "")
+
+    def write_reg(ident, reg, prim_addr, prim_size, prefix, suffix):
+        addr = hex(reg.addr) if prim_addr is None else prim_addr
+        size = reg.size if prim_size is None else prim_size
+
+        addr_ret = out(f"{ident}_{prefix}BASE_ADDRESS{suffix}", addr)
+        if size is not None and size != 0:
+            size_ret = out(f"{ident}_{prefix}SIZE{suffix}", size)
         else:
-            ident = base_ident
+            size_ret = None
 
-        out_node(node, ident, val,
-                 # Name alias from 'reg-names = ...'
-                 f"{str2ident(reg.name)}_{base_ident}" if reg.name else None)
-
-    for reg in node.regs:
-        write_reg(reg, "BASE_ADDRESS", hex(reg.addr))
-        if reg.size:
-            write_reg(reg, "SIZE", reg.size)
+        return (addr_ret, size_ret)
 
+    out_comment("BASE_ADDRESS and SIZE macros from the 'reg' property",
+                blank_before=False)
+    for_each_ident(node, write_regs_for_ident)
 
 def write_props(node):
     # Writes any properties defined in the "properties" section of the binding