Incorporated the review comments

Author: rajkan01

docs/porting/target/tickless/resources/Normal_Tick.png

@@ -18,11 +18,20 @@ To support tickless mode in Mbed OS, your target needs to meet two requirements:
 - Support for Sleep HAL API
 - Support for either Low Power or Microsecond Ticker HAL API
 
-To enable tickless mode for your target, add the `MBED_TICKLESS` macro in target.json > your target's section > macro options.
-
-When the tickless mode is enabled, the device default SysTick mechanism overrides by the [OsTimer](../mbed-os-api-doxy/structos__timer__def.html) implementation based on either the [low power ticker](../mbed-os-api-doxy/group__hal__lp__ticker.html) or [microsecond ticker](../mbed-os-api-doxy/group__hal__us__ticker.html).
-
-By default, tickless mode uses the low-power ticker (if available). If a target's low-power ticker has an excessively long wake-up time or other performance issues, make it use the microsecond ticker instead: set `tickless-from-us-ticker` to `true` in target.json > your target's section.
+To enable tickless mode for your target, add the `MBED_TICKLESS` macro in `target.json` of your target's section as follows:
+```json
+"macros_add": [
+    "MBED_TICKLESS"
+]
+```
+
+When tickless mode is enabled, Mbed OS's default [OsTimer](../mbed-os-api-doxy/structos__timer__def.html) based on the [low power ticker](../mbed-os-api-doxy/group__hal__lp__ticker.html) replaces SysTick. If a target's low power ticker has an excessively long wake-up time or other performance issues, make it use the [microsecond ticker](../mbed-os-api-doxy/group__hal__us__ticker.html) instead by adding the below configuration in 'target.json' of your target's section. And this configuration is not required for the target which does not have low power ticker as the default OsTimer based on the microsecond ticker.
+
+```json
+"overrides": {
+    "tickless-from-us-ticker": true
+}
+```
 
 If tickless mode uses the microsecond ticker, the device will enter sleep rather than deep sleep, but will still avoid unnecessary tick calls.