diff --git a/plat/rpi3/platform.mk b/plat/rpi3/platform.mk
index 36c1ee2..07d2bf1 100644
--- a/plat/rpi3/platform.mk
+++ b/plat/rpi3/platform.mk
@@ -109,6 +109,10 @@
 # Assume that BL33 isn't the Linux kernel by default
 RPI3_DIRECT_LINUX_BOOT		:= 0
 
+# UART to use at runtime. -1 means the runtime UART is disabled.
+# Any other value means the default UART will be used.
+RPI3_RUNTIME_UART               := -1
+
 # BL32 location
 RPI3_BL32_RAM_LOCATION	:= tdram
 ifeq (${RPI3_BL32_RAM_LOCATION}, tsram)
@@ -126,6 +130,7 @@
 $(eval $(call add_define,RPI3_BL33_IN_AARCH32))
 $(eval $(call add_define,RPI3_DIRECT_LINUX_BOOT))
 $(eval $(call add_define,RPI3_PRELOADED_DTB_BASE))
+$(eval $(call add_define,RPI3_RUNTIME_UART))
 
 # Verify build config
 # -------------------