Added links to examples in API documentation

docs/api/system/deep_sleep.rst

@@ -87,3 +87,8 @@ The following function can be used to enter deep sleep once wakeup sources are c
 
 .. doxygenfunction:: esp_deep_sleep_start
 
+Application Example
+-------------------
+ 
+Implementation of basic functionality of deep sleep is shown in `protocols/sntp <https://github.com/espressif/esp-idf/tree/master/examples/protocols/sntp>`_ example, where ESP module is periodically waken up to retrive time from NTP server.
+

docs/api/system/log.rst

@@ -3,9 +3,11 @@
 Application Example
 -------------------
 
-`Instructions`_
-
-.. _Instructions: ../template.html
+Log library is commonly used by most of esp-idf components and examples. For demonstration of log functionality check `examples <https://github.com/espressif/esp-idf/tree/master/examples>`_ folder of `espressif/esp-idf <https://github.com/espressif/esp-idf>`_ repository, that among others, contains the following examples:
+ 
+* `system/ota <https://github.com/espressif/esp-idf/tree/master/examples/system/ota>`_ 
+* `storage/sd_card <https://github.com/espressif/esp-idf/tree/master/examples/storage/sd_card>`_ 
+* `protocols/https_request <https://github.com/espressif/esp-idf/tree/master/examples/protocols/https_request>`_ 
 
 API Reference
 -------------

docs/api/system/ota.rst

@@ -1,6 +1,11 @@
 OTA
 ===
 
+Application Example
+-------------------
+ 
+Demonstration of OTA (over the air) firmware update workflow: `examples/system/ota <https://github.com/espressif/esp-idf/tree/master/examples/system/ota>`_.
+
 API Reference
 -------------