docs(uart): clarify example pins need a USB-to-UART bridge

docs/en/api-guides/stdio.rst

@@ -26,6 +26,10 @@ On {IDF_TARGET_NAME}, ESP-IDF provides implementations of VFS drivers for I/O ov
 
 Standard I/O is not limited to these options, though. See below on enabling custom destinations for standard I/O.
 
+.. note::
+
+    The console path is separate from an application UART that you open with the :doc:`UART driver <../api-reference/peripherals/uart>` on other pins. If a UART peripheral provides console output, a USB-to-UART bridge chip is required. Many development boards already include this bridge chip onboard for console communication between the PC and the default UART0. If a USB or USB Serial/JTAG peripheral provides console output, no adapter chip is needed. The USB connector on the development board connects directly to the chip's USB D+/D- pins. Traffic on other UART ports does not appear in ``idf.py monitor`` unless a given port is configured as the console. For details, see :doc:`Establish Serial Connection with {IDF_TARGET_NAME} <../get-started/establish-serial-connection>`.
+
 Configuration
 -------------
 

docs/en/api-reference/peripherals/uart.rst

@@ -150,6 +150,9 @@ The same macro :c:macro:`UART_PIN_NO_CHANGE` should be specified for pins that w
   // Set UART pins(TX: IO4, RX: IO5, RTS: IO18, CTS: IO19, DTR: UNUSED, DSR: UNUSED)
   ESP_ERROR_CHECK(uart_set_pin({IDF_TARGET_UART_EXAMPLE_PORT}, 4, 5, 18, 19, UART_PIN_NO_CHANGE, UART_PIN_NO_CHANGE));
 
+.. note::
+
+    The pin numbers above are only an example. On many development boards, the onboard USB-to-UART bridge is connected to the UART0 default TX/RX pins. If you need to communicate with a PC over other ports or pins, connect a separate USB-to-UART bridge to those pins.
 
 .. _uart-api-running-uart-communication:
 

docs/en/get-started/establish-serial-connection.rst

@@ -20,6 +20,8 @@ Some development boards have the USB-to-UART bridge installed. If a board does n
 
     The {IDF_TARGET_NAME} supports the USB peripheral. In this case, the USB-to-UART bridge is not needed and the device can be flashed directly.
 
+    The USB peripheral and its USB PHY are separate from the UART controllers. UART controllers output UART signals on GPIOs, so connecting a UART to a PC over USB still requires an onboard or external USB-to-UART bridge.
+
     .. blockdiag::
         :scale: 70%
         :caption: SoC with Supported USB