docs: mention ESP32 ECO3 in relation to PSRAM cache workarounds

docs/en/api-guides/external-ram.rst

@@ -131,3 +131,4 @@ External RAM use has the following restrictions:
     .. include:: inc/external-ram-esp32-notes.rst
 
 .. _ESP32 ECO: https://www.espressif.com/sites/default/files/documentation/eco_and_workarounds_for_bugs_in_esp32_en.pdf
+.. _ESP32 ECO V3 User Guide: https://www.espressif.com/sites/default/files/documentation/ESP32_ECO_V3_User_Guide__EN.pdf

docs/en/api-guides/inc/external-ram-esp32-notes.rst

@@ -21,3 +21,8 @@ Aside from linking to a recompiled version of Newlib with the additional flag, E
 
 - Avoids using some ROM functions
 - Allocates static memory for the WiFi stack
+
+ESP32 rev v3
+------------
+
+ESP32 revision 3 ("ECO V3") fixes the PSRAM cache issue found in rev. 1. When :ref:`CONFIG_ESP32_REV_MIN` option is set to rev. 3, compiler workarounds related to PSRAM will be disabled. For more information about ESP32 ECO V3, see `ESP32 ECO V3 User Guide`_.