esp32: Add support to build with ESP-IDF v4.2.

Signed-off-by: Damien George <damien@micropython.org>

ports/esp32/README.md

@@ -28,7 +28,7 @@ manage the ESP32 microcontroller, as well as a way to manage the required
 build environment and toolchains needed to build the firmware.
 
 The ESP-IDF changes quickly and MicroPython only supports certain versions.
-Currently MicroPython supports v4.0.2 and v4.1.1,
+Currently MicroPython supports v4.0.2, v4.1.1 and v4.2,
 although other IDF v4 versions may also work.
 
 To install the ESP-IDF the full instructions can be found at the

ports/esp32/main/CMakeLists.txt

@@ -108,6 +108,11 @@ if(IDF_VERSION_MINOR GREATER_EQUAL 1)
     list(APPEND IDF_COMPONENTS esp_netif)
 endif()
 
+if(IDF_VERSION_MINOR GREATER_EQUAL 2)
+    list(APPEND IDF_COMPONENTS esp_system)
+    list(APPEND IDF_COMPONENTS esp_timer)
+endif()
+
 # Register the main IDF component.
 idf_component_register(
     SRCS
@@ -169,5 +174,12 @@ foreach(comp ${IDF_COMPONENTS})
     endif()
 endforeach()
 
+if(IDF_VERSION_MINOR GREATER_EQUAL 2)
+    # These paths cannot currently be found by the IDF_COMPONENTS search loop above,
+    # so add them explicitly.
+    list(APPEND MICROPY_CPP_INC_EXTRA ${IDF_PATH}/components/soc/soc/${IDF_TARGET}/include)
+    list(APPEND MICROPY_CPP_INC_EXTRA ${IDF_PATH}/components/soc/soc/include)
+endif()
+
 # Include the main MicroPython cmake rules.
 include(${MICROPY_DIR}/py/mkrules.cmake)