doc: sort all stdio implementations into sys_stdio group

cpu/esp32/doc.txt

@@ -6,6 +6,21 @@
  * directory for more details.
  */
 
+/**
+ * @defgroup     stdio_usb_serial_jtag  STDIO over ESP32 Debug Serial/JTAG
+ * @ingroup      sys_stdio
+ * @brief        STDIO via the USB Serial/JTAG debug interface found on some ESP32 SoCs
+ *
+ * Some members of the ESP32 family (ESP32-C3, ESP32-S3, ESP32-H2) provide a on-chip
+ * debug interface that provides a serial console and JTAG via USB.
+ *
+ * To route STDIO to this debug console, enable this module.
+ *
+ *     USEMODULE += stdio_usb_serial_jtag
+ *
+ * @see          cpu_esp32
+ */
+
 /**
 @defgroup   cpu_esp32 ESP32 SoC Series
 @ingroup    cpu

cpu/native/include/native_internal.h

@@ -10,6 +10,17 @@
  * Native CPU internal declarations
  */
 
+/**
+ * @defgroup    cpu_native_stdio    STDIO for native
+ * @ingroup     sys_stdio
+ * @brief       Standard input/output backend for native
+ *
+ * This will hook up RIOT's stdio to the host's stdio fds. It is the default
+ * stdio implementation of the board `native`.
+ *
+ * @see         cpu_native
+ */
+
 /**
  * @ingroup    cpu_native
  * @{

drivers/include/ethos.h

@@ -6,6 +6,21 @@
  * details.
  */
 
+/**
+ * @defgroup    drivers_ethos_stdio   STDIO via ethos
+ * @ingroup     sys_stdio
+ * @brief       Standard input/output backend multiplexed via ethernet-over-serial
+ *
+ * This will multiplex STDIO via ethos.
+ * The shell can be accessed via the `ethos` tool.
+ *
+ * To enable this stdio implementation, select
+ *
+ *     USEMODULE += stdio_ethos
+ *
+ * @see         drivers_ethos
+ */
+
 /**
  * @defgroup    drivers_ethos Ethernet-over-serial driver
  * @ingroup     drivers_netdev

drivers/include/slipdev.h

@@ -6,6 +6,21 @@
  * directory for more details.
  */
 
+/**
+ * @defgroup    drivers_slipdev_stdio   STDIO via SLIP
+ * @ingroup     sys_stdio
+ * @brief       Standard input/output backend multiplexed via SLIP
+ *
+ * This will multiplex STDIO via the Serial Line Internet Protocol.
+ * The shell can be accessed via the `sliptty` tool.
+ *
+ * To enable this stdio implementation, select
+ *
+ *     USEMODULE += slipdev_stdio
+ *
+ * @see         drivers_slipdev
+ */
+
 /**
  * @defgroup    drivers_slipdev SLIP network device
  * @ingroup     drivers_netdev

pkg/tinyusb/doc.txt

@@ -129,3 +129,14 @@
  * [tinyUSB documentation](https://docs.tinyusb.org/en/latest/reference/getting_started.html)
  * for details.
  */
+
+/**
+ * @defgroup     pkg_tinyusb_stdio_cdc_acm STDIO over USB CDC-ACM (tinyUSB)
+ * @ingroup      sys_stdio
+ * @brief        Standard input/output backend using tinyUSB CDC ACM
+ * @see          pkg_tinyusb
+ *
+ * To enable this, select the `tinyusb_stdio_cdc_acm` module:
+ *
+ *     USEMODULE += stdio_tinyusb_cdc_acm
+ */

sys/include/net/telnet.h

@@ -6,6 +6,26 @@
  * directory for more details.
  */
 
+/**
+ * @defgroup    net_telnet_stdio    STDIO over telnet
+ * @ingroup     sys_stdio
+ * @brief       Standard input/output via telnet
+ *
+ * This will make RIOT's stdio available over telnet.
+ *
+ * To enable it, add
+ *
+ *     USEMODULE += stdio_telnet
+ *
+ * to your application.
+ * You will also have to set `I_UNDERSTAND_THAT_TELNET_IS_INSECURE = 1` to
+ * acknowledge that you will only use this for debugging in an isolated network.
+ *
+ * You can then use any standard `telnet` client to connect to your node.
+ *
+ * @see         net_telnet
+ */
+
 /**
  * @defgroup    net_telnet basic Telnet server implementation
  * @ingroup     net_ipv6

sys/include/stdio_nimble.h

@@ -8,7 +8,11 @@
 
 /**
  * @defgroup     sys_stdio_nimble STDIO over NimBLE
- * @ingroup      sys
+ * @ingroup      sys_stdio
+ *
+ * To enable stdio over nimBLE, add the module `stdio_nimble`:
+ *
+ *     USEMODULE += stdio_nimble
  *
  * @experimental This feature is experimental as some use-cases, such as examples/twr_aloha, show
  *               unexpected behaviour.

sys/include/stdio_rtt.h

@@ -9,10 +9,17 @@
 
 /**
  * @defgroup    sys_stdio_rtt STDIO over SEGGER RTT
- * @ingroup     sys
+ * @ingroup     sys_stdio
  *
  * @brief       STDIO mapping for running the STDIO over SEGGER's RTT interface
  *
+ * To enable stdio over SEGGER's RTT, enable the module `stdio_rtt`:
+ *
+ *     USEMODULE += stdio_rtt
+ *
+ * @note    Currently, `stdio_rtt` is only supported when OpenOCD or J-Link is
+ *          used as programmer.
+ *
  * @{
  * @file
  *

sys/include/stdio_semihosting.h

@@ -8,7 +8,7 @@
 
 /**
  * @defgroup    sys_stdio_semihosting STDIO over Semihosting
- * @ingroup     sys
+ * @ingroup     sys_stdio
  *
  * @brief       Standard input/output backend using ARM Semihosting
  *

sys/include/stdio_uart.h

@@ -9,10 +9,17 @@
 
 /**
  * @defgroup    sys_stdio_uart STDIO over UART
- * @ingroup     sys
+ * @ingroup     sys_stdio
  *
  * @brief       Standard input/output backend using UART
  *
+ * To enable stdio over UART, enable the `stdio_uart` module:
+ *
+ *     USEMODULE += stdio_uart
+ *
+ * @note    For many board, `stdio_uart` is already the default stdio backend
+ *          and therefore already enabled.
+ *
  * ## Input
  *
  * @warning Standard input is disabled by default on UART. To enable it, load

sys/include/usb/usbus/cdc/acm.h

@@ -6,6 +6,19 @@
  * more details.
  */
 
+/**
+ * @defgroup    usbus_cdc_acm_stdio  STDIO over CDC ACM (usbus)
+ * @ingroup     sys_stdio
+ * @brief       Standard input/output backend using usbus CDC ACM.
+ *
+ * This will provide STDIO via a virtual COM port over USB.
+ * It can be enabled with
+ *
+ *    USEMODULE += stdio_cdc_acm
+ *
+ * @see         usbus_cdc_acm
+ */
+
 /**
  * @defgroup    usbus_cdc_acm USBUS CDC ACM - USBUS CDC abstract control model
  * @ingroup     usb

sys/net/application_layer/telnet/stdio_telnet.c

@@ -7,7 +7,8 @@
  */
 
 /**
- * @ingroup     sys
+ * @defgroup    net_telnet_stdio    STDIO via telnet
+ * @ingroup     sys_stdio
  * @{
  *
  * @file

sys/stdio_null/doc.txt

@@ -0,0 +1,21 @@
+/*
+ * Copyright (C) 2019 Bas Stottelaar <[email protected]>
+ *
+ * This file is subject to the terms and conditions of the GNU Lesser
+ * General Public License v2.1. See the file LICENSE in the top level
+ * directory for more details.
+ */
+
+/**
+ * @defgroup    sys_stdio_null  STDIO null driver
+ * @ingroup     sys_stdio
+ *
+ * @brief       Dummy implementation of the stdio interface.
+ *
+ * This provides a null driver for STDIO that does not depend on anything.
+ * It is a mock implementation that will never output / read anything.
+ *
+ * To enable it use
+ *
+ *     USEMODULE += stdio_null
+ */

sys/stdio_null/stdio_null.c

@@ -7,7 +7,7 @@
  */
 
 /**
- * @ingroup     sys
+ * @ingroup     sys_stdio_null
  * @{
  *
  * @file