[posix] replace RCP vendor extension find package with include command

src/posix/platform/FindExampleVendorDeps.cmake

@@ -36,9 +36,7 @@ files used by a vendor implementation in the posix library.
 
 The name of this file and the name of the targets it defines are
 conventionally related. For the purpose of this reference, targets
-will be based off of the identifier "ExampleRcpVendorDeps". Derived
-references should be based off of the value of the cache variable,
-"OT_POSIX_CONFIG_RCP_VENDOR_DEPS_PACKAGE".
+will be based off of the identifier "ExampleRcpVendorDeps".
 
 For more information about package resolution using CMake find modules,
 reference the cmake-developer documentation.

src/posix/platform/vendor.cmake

@@ -30,7 +30,10 @@ set(OT_POSIX_CONFIG_RCP_VENDOR_INTERFACE "vendor_interface_example.cpp"
     CACHE STRING "vendor interface implementation")
 
 set(OT_POSIX_CONFIG_RCP_VENDOR_DEPS_PACKAGE "" CACHE STRING
-    "name of optional external package to link to rcp vendor implementation")
+    "path to CMake file to define and link posix vendor extension")
+
+set(OT_POSIX_RCP_VENDOR_TARGET "" CACHE STRING 
+    "name of vendor extension CMake target to link with posix library")
 
 if(OT_POSIX_CONFIG_RCP_BUS STREQUAL "VENDOR")
     add_library(rcp-vendor-intf ${OT_POSIX_CONFIG_RCP_VENDOR_INTERFACE})
@@ -50,11 +53,9 @@ if(OT_POSIX_CONFIG_RCP_BUS STREQUAL "VENDOR")
     target_link_libraries(openthread-posix PUBLIC rcp-vendor-intf)
 
     if (OT_POSIX_CONFIG_RCP_VENDOR_DEPS_PACKAGE)
-        set(DEPS_TARGET ${OT_POSIX_CONFIG_RCP_VENDOR_DEPS_PACKAGE}::${OT_POSIX_CONFIG_RCP_VENDOR_DEPS_PACKAGE})
-        find_package(${OT_POSIX_CONFIG_RCP_VENDOR_DEPS_PACKAGE})
-
-        if(${OT_POSIX_CONFIG_RCP_VENDOR_DEPS_PACKAGE}_FOUND)
-            target_link_libraries(rcp-vendor-intf PUBLIC ${DEPS_TARGET})
+        include(${OT_POSIX_CONFIG_RCP_VENDOR_DEPS_PACKAGE})
+        if (OT_POSIX_CONFIG_RCP_VENDOR_TARGET)
+            target_link_libraries(rcp-vendor-intf PRIVATE ${OT_POSIX_RCP_VENDOR_TARGET})
         endif()
     endif()
 endif()

src/posix/platform/vendor_extension_example.cmake

@@ -0,0 +1,57 @@
+#
+#  Copyright (c) 2023, The OpenThread Authors.
+#  All rights reserved.
+#
+#  Redistribution and use in source and binary forms, with or without
+#  modification, are permitted provided that the following conditions are met:
+#  1. Redistributions of source code must retain the above copyright
+#     notice, this list of conditions and the following disclaimer.
+#  2. Redistributions in binary form must reproduce the above copyright
+#     notice, this list of conditions and the following disclaimer in the
+#     documentation and/or other materials provided with the distribution.
+#  3. Neither the name of the copyright holder nor the
+#     names of its contributors may be used to endorse or promote products
+#     derived from this software without specific prior written permission.
+#
+#  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+#  AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+#  IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+#  ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
+#  LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+#  CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+#  SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+#  INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+#  CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+#  ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+#  POSSIBILITY OF SUCH DAMAGE.
+#
+
+# This file provides an example on how to implement a RCP vendor extension.
+
+# Set name of the cmake target to link with rcp-vendor-intf
+set(OT_POSIX_RCP_VENDOR_TARGET "vendor-lib")
+
+# Create library target using source file "vendor_source.cpp"
+add_library(${OT_POSIX_RCP_VENDOR_TARGET} vendor_source.cpp)
+
+# Include header files located at "${VENDOR_INCLUDE_PATH}"
+target_include_directories(${OT_POSIX_RCP_VENDOR_TARGET}
+    PRIVATE
+        ${VENDOR_INCLUDE_PATH}
+)
+
+set(EXAMPLE_DEPS_ENABLE OFF CACHE BOOL "Include example deps library if enabled")
+
+# Search for and include an optional library using the module file
+# "FindExampleRcpDeps.cmake" at path "${VENDOR_MODULE_PATH}"
+if (EXAMPLE_DEPS_ENABLE)
+    list(APPEND CMAKE_MODULE_PATH ${VENDOR_MODULE_PATH})
+    find_package(ExampleRcpVendorDeps)
+
+    if(ExampleRcpVendorDeps_FOUND)
+        target_link_libraries(${OT_POSIX_RCP_VENDOR_TARGET} 
+            PRIVATE
+            ${ExampleRcpVendorDeps::ExampleRcpVendorDeps}
+        )
+    endif()
+endif()