Add a Mailbox interface

Change-Id: If68e70709c496849cb781af5f7288fa3f7ddcdb5
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 0487b44..3e14fe0 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -58,5 +58,8 @@
 # Build applications
 add_subdirectory(applications)
 
+# Build drivers
+add_subdirectory(drivers)
+
 # Merge libraries into static library
-target_link_libraries(ethosu_core INTERFACE tflu cmsis_core cmsis_device ethosu_applications)
+target_link_libraries(ethosu_core INTERFACE tflu cmsis_core cmsis_device ethosu_applications ethosu_drivers)