Merge branch 'feature/Add_noinit_rtc_noinit_sections' into 'master'

esp32: Add .noinit and .rtc_noinit sections to the linker script

See merge request idf/esp-idf!1996

docs/en/api-guides/general-notes.rst

@@ -111,6 +111,12 @@ Constant data may also be placed into DRAM, for example if it is used in an ISR
 
 Needless to say, it is not advised to use ``printf`` and other output functions in ISRs. For debugging purposes, use ``ESP_EARLY_LOGx`` macros when logging from ISRs. Make sure that both ``TAG`` and format string are placed into ``DRAM`` in that case.
 
+The macro ``__NOINIT_ATTR`` can be used as attribute to place data into ``.noinit`` section. The values placed into this section will not be initialized at startup and keep its value after software restart.
+
+Example::
+
+    __NOINIT_ATTR uint32_t noinit_data;
+
 DROM (data stored in Flash)
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
@@ -121,6 +127,12 @@ RTC slow memory
 
 Global and static variables used by code which runs from RTC memory (i.e. deep sleep stub code) must be placed into RTC slow memory. Please check detailed description in :doc:`deep sleep <deep-sleep-stub>` documentation.
 
+The attribute macro named ``RTC_NOINIT_ATTR`` can be used to place data into this type of memory. The values placed into this section keep their value after waking from deep sleep.
+
+Example::
+
+    RTC_NOINIT_ATTR uint32_t rtc_noinit_data;
+
 DMA Capable Requirement
 -----------------------