doc: Misc improvements

Doing small updates:
- Add doc building
- Add missing Kconfig description to Configuration page
- Improvements to logging
- Remove release plan before v1.0.0

Signed-off-by: Tommi Rantanen <tommi.rantanen@nordicsemi.no>

Author: trantanen

README.md

@@ -4,10 +4,3 @@ The Serial Modem contains the Serial Modem application for nRF91-based devices,
 It includes host examples in the form of the Serial Modem AT Client library and the Serial Modem AT Client Shell sample.
 
 You can find the documentation in the [Serial Modem] (https://docs.nordicsemi.com/bundle/addon-serial_modem-latest/page/index.html) documentation.
-
-Serial Modem release plan looks as follows:
-
-* v0.3.0: 19-Dec-2025
-  * Aligns with NCS 3.2.0 release meaning SM v0.3.0 will be released 1-10 days after the NCS
-* v1.0.0: 20-Feb-2026
-  * Official Serial Modem release after which changes in v1.x.x releases are backwards compatible

doc/app/sm_build_and_run.rst

@@ -215,7 +215,7 @@ Using the LwM2M carrier library
 The application supports the |NCS| `LwM2M carrier`_ library that you can use to connect to the operator's device management platform.
 See the library's documentation for more information and configuration options.
 
-To enable the LwM2M carrier library, add the parameter ``-DOVERLAY_CONFIG=overlay-carrier.conf`` to your build command.
+To enable the LwM2M carrier library, add the parameter ``-DEXTRA_CONF_FILE=overlay-carrier.conf`` to your build command.
 
 The CA root certificates that are needed for modem FOTA are not provisioned in the |SM| application.
 You can flash the `Cellular: LwM2M carrier`_ sample to write the certificates to modem before flashing the |SM| application, or use the `Cellular: AT Client`_ sample as explained in `preparing the Cellular: LwM2M Client sample for production <lwm2m_client_provisioning_>`_.

doc/app/sm_configuration.rst

@@ -203,6 +203,14 @@ CONFIG_SM_UART_TX_BUF_SIZE - Send buffer size for UART.
    This option defines the size of the buffer for sending (TX) UART traffic.
    The default value is 256.
 
+.. _CONFIG_SM_URC_BUFFER_SIZE:
+
+CONFIG_SM_URC_BUFFER_SIZE - URC buffer size.
+   Buffer, in which unsolicited result codes (URC) are stored before being sent to the host.
+   The buffer has to be large enough to hold the largest URC that can be sent by the modem.
+   Result codes longer than this size will get dropped.
+   The default value is 4096.
+
 .. _CONFIG_SM_PPP_FALLBACK_MTU:
 
 CONFIG_SM_PPP_FALLBACK_MTU - Control the MTU used by PPP.

doc/app/sm_logging.rst

@@ -31,20 +31,51 @@ To switch to ``UART0`` output for application logs, change the following options
    CONFIG_LOG_BACKEND_RTT=n
    CONFIG_LOG_BACKEND_UART=y
 
+The default logging level for the |SM| is ``CONFIG_SM_LOG_LEVEL_INF``.
+You can get more verbose logs by setting the ``CONFIG_SM_LOG_LEVEL_DBG`` Kconfig option.
+
+TF-M logging must use the same UART as the application. For more details, see `shared TF-M logging`_.
+
 Modem traces
 ************
 
 To send modem traces over UART on an nRF91 Series DK, configuration must be added for the UART device in the devicetree and Kconfig.
-This is done by adding the `modem trace UART snippet`_ when building and programming.
+This is done by adding the `modem trace UART snippet`_ (``-Dapp_SNIPPET=nrf91-modem-trace-uart``) when building and programming.
 
 Use the `Cellular Monitor app`_ for capturing and analyzing modem traces.
 
-TF-M logging must use the same UART as the application. For more details, see `shared TF-M logging`_.
+.. note::
+
+   When measuring power consumption while the modem is active, the modem traces must not be active.
+   If the build includes modem traces, the traces must be deactivated with ``AT%XMODEMTRACE=0``, before taking measurements.
+   Active traces show ~700 uA overhead on the power consumption.
+
+   If HW flow control is enabled for the trace UART (it is not by default), the same ~700uA overhead is present even when the traces are deactivated with ``AT%XMODEMTRACE=0``.
+   HW flow control prevents the trace UART from sending, when there is no reader for the data.
+   This in turn prevents the trace UART from suspending as it cannot empty its buffers.
+
+.. note::
+
+   Modem traces captured through UART are corrupted if application logs through RTT are simultaneously captured.
+   When capturing modem traces through UART with the `Cellular Monitor app`_ and simultaneously capturing RTT logs, for example, with J-Link RTT Viewer, the modem trace misses packets, and captured packets might have incorrect information.
+
+   If you need to capture modem traces and RTT logs at the same time, enable HW flow control for modem trace UART.
+   This can be done for the `nRF9151 DK <nrf9151dk_>`_ by adding the following change to :file:`app/boards/nrf9151dk_nrf9151_ns.overlay`:
+
+   .. parsed-literal::
+      :class: highlight
+
+      &uart1 {
+       hw-flow-control;
+      };
+
+   Otherwise, you can choose not to capture RTT logs.
+   Having only RTT logs enabled does not cause this issue.
 
 .. _sm_modem_trace_cmux:
 
-Collecting modem traces through CMUX backend
-********************************************
+Modem traces through CMUX
+*************************
 
 The |SM| application supports collecting modem traces through the CMUX multiplexer.
 When enabled, modem traces are sent through a dedicated CMUX channel, allowing simultaneous AT commands, PPP data, and trace collection over the same serial port.

doc/gsg_guide.rst

@@ -70,6 +70,10 @@ Complete the following steps for building and running:
 
       west build -p -b nrf9151dk/nrf9151/ns
 
+   To build the application with Kconfig and DTC overlays and extra Kconfig options, the following command gives an example of how they are passed as build arguments::
+
+      west build -p -b nrf9151dk/nrf9151/ns -- -DEXTRA_CONF_FILE="overlay-ppp.conf;overlay-cmux.conf" -DEXTRA_DTC_OVERLAY_FILE="overlay-external-mcu.overlay" -DCONFIG_SM_LOG_LEVEL_DBG=y
+
 #. To program the application, run the following command::
 
       west flash