Merge branch 'docs/add_ethernet_intro' into 'master'

docs: add ESP-IDF Ethernet guide reference to ESP-AT Ethernet documentation

See merge request application/esp-at!1952

Author: xcguang

docs/en/Compile_and_Develop/How_to_enable_ESP_AT_Ethernet.rst

@@ -8,6 +8,10 @@ Overview
 
 This document is intended to help you enable ESP-AT Ethernet. After that, a simple test will show you how to confirm whether the enablement is successful.
 
+.. note::
+
+  For more technical details about Ethernet (including basic concepts, MAC/PHY configuration, clock configuration, driver installation, and more), please refer to the `ESP-IDF Ethernet Programming Guide <https://docs.espressif.com/projects/esp-idf/en/latest/{IDF_TARGET_PATH_NAME}/api-reference/network/esp_eth.html>`__.
+
 Step 1. Configure and Flash
 -----------------------------
 

docs/zh_CN/Compile_and_Develop/How_to_enable_ESP_AT_Ethernet.rst

@@ -8,6 +8,10 @@
 
 本文档旨在指导用户启用 ESP-AT Ethernet，并通过简单的测试，展示如何确认是否启用成功。
 
+.. note::
+
+  如需了解更多关于以太网的技术细节（包括基本概念、MAC/PHY 配置、时钟配置、驱动程序安装等），请参考 `ESP-IDF 以太网编程指南 <https://docs.espressif.com/projects/esp-idf/zh_CN/latest/{IDF_TARGET_PATH_NAME}/api-reference/network/esp_eth.html>`__。
+
 第一步：配置并烧录
 -----------------------