drivers/rmt: Implement an upper-half RMT character driver

The RMT (Remote Control) character driver allows to use the RMT
peripheral (usually, a one-wire peripheral dedicated to driving
IR remote control) as a character driver.

Please note that this perpiheral depends on the lower-half specific
driver implementation.

drivers/rmt/CMakeLists.txt

@@ -0,0 +1,29 @@
+# ##############################################################################
+# drivers/rmt/CMakeLists.txt
+#
+# Licensed to the Apache Software Foundation (ASF) under one or more contributor
+# license agreements.  See the NOTICE file distributed with this work for
+# additional information regarding copyright ownership.  The ASF licenses this
+# file to you under the Apache License, Version 2.0 (the "License"); you may not
+# use this file except in compliance with the License.  You may obtain a copy of
+# the License at
+#
+# http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.  See the
+# License for the specific language governing permissions and limitations under
+# the License.
+#
+# ##############################################################################
+
+if(CONFIG_RMT)
+  set(SRCS)
+
+  if(CONFIG_RMTCHAR)
+    list(APPEND SRCS rmtchar.c)
+  endif()
+
+  target_sources(drivers PRIVATE ${SRCS})
+endif()