doc: Add documentation for PPP modem shell sample

Add documentation for PPP modem shell sample and move sample
descriptions to own index page.

Signed-off-by: Seppo Takalo <seppo.takalo@nordicsemi.no>

Author: SeppoTakalo

doc/app/sm_description.rst

@@ -374,7 +374,7 @@ Connecting with an external MCU
    This section does not apply to Thingy:91 X.
 
 If you run your user application on an external MCU (for example, an nRF52 Series development kit), you can control the |SM| application on an nRF91 Series device directly from the application.
-See the :ref:`sm_shell_sample` for a sample implementation of such an application.
+See the :ref:`sm_at_client_shell` for a sample implementation of such an application.
 
 To connect with an external MCU using UART_2, include the :file:`overlay-external-mcu.overlay` devicetree overlay in your build.
 This overlay configures the UART_2 pins, DTR pin, and RI pin for the nRF9151 DK.
@@ -453,7 +453,7 @@ The following table shows how to connect selected development kit to an nRF91 Se
            - GPIO GND
 
       .. note::
-         You must disable the VCOM0 on the nRF54L15 DK to release the UART GPIO pins to use it with the :ref:`sm_shell_sample`.
+         You must disable the VCOM0 on the nRF54L15 DK to release the UART GPIO pins to use it with the :ref:`sm_samples`.
 
          * For nRF54L15 DK, you can use the `Board Configurator app`_ to disable the `Connect port VCOM0` setting.
 
@@ -522,7 +522,7 @@ Use the following UART devices:
 * nRF91 Series DK - UART2
 
 The UART configuration must match on both sides.
-By default the |SM| application and :ref:`sm_shell_sample` use the following settings:
+By default the |SM| application and :ref:`sm_samples` use the following settings:
 
 * Hardware flow control: enabled
 * Baud rate: 115200

doc/app/sm_dtr_ri.rst

@@ -61,4 +61,4 @@ The following image illustrates the DTR and RI signal behavior in relation to th
 
    DTR/RI signal diagram
 
-The :ref:`sm_shell_sample` sample and :ref:`lib_sm_at_client` library show an example of how to use DTR and RI signals in an external MCU application.
+The :ref:`sm_samples` and :ref:`lib_sm_at_client` library show an example of how to use DTR and RI signals in an external MCU application.

doc/images/samples_overview.svg

@@ -13,7 +13,7 @@ It includes host examples in the form of the |SM| AT Client library and the |SM|
 
    gsg_guide
    app/README
-   samples/sm_at_client_shell
+   samples/README
    drivers/dtr_uart
    lib/sm_at_client
    migration_notes

doc/index.rst

@@ -82,6 +82,12 @@
 .. _`Serial Terminal app`: https://docs.nordicsemi.com/bundle/nrf-connect-serial-terminal/page/index.html
 .. _`Board Configurator app`: https://docs.nordicsemi.com/bundle/nrf-connect-board-configurator/page/index.html
 
+.. ### docs.zephyrproject.org/
+
+.. _`Zephyr Networking`: https://docs.zephyrproject.org/latest/connectivity/networking/index.html
+.. _`Zephyr Network APIs`: https://docs.zephyrproject.org/latest/connectivity/networking/api/apis.html
+.. _`Zephyr Modem modules`: https://docs.zephyrproject.org/latest/services/modem/index.html
+
 .. ### github.com
 
 .. _`github_release`: https://github.com/nrfconnect/ncs-serial-modem/releases
@@ -91,7 +97,6 @@
 .. ### others
 
 .. _`Private addresses`: https://en.wikipedia.org/wiki/IP_address#Private_addresses
-.. _`Zephyr Network APIs`: https://docs.zephyrproject.org/latest/connectivity/networking/api/apis.html#network-apis
 
 .. _`3GPP TS 27.010`: https://www.etsi.org/deliver/etsi_ts/127000_127099/127010/18.00.00_60/ts_127010v180000p.pdf
 .. _`3GPP TS 27.007`: https://www.etsi.org/deliver/etsi_ts/127000_127099/127007/18.06.00_60/ts_127007v180600p.pdf

doc/links.txt

@@ -0,0 +1,37 @@
+.. _sm_samples:
+
+|SM| host samples
+#################
+
+The |SM| includes sample applications that demonstrate how to interact with the |SM| application running on an nRF91 Series device.
+These samples showcase different integration approaches for controlling the nRF91 Series SiP as a cellular modem.
+
+.. figure:: ../images/samples_overview.svg
+   :alt: Serial Modem samples overview
+
+   Serial Modem running on nRF91 Series DK with a host sample application on an external MCU
+
+Use the :ref:`sm_at_client_shell` when:
+
+* You need direct AT command control
+* Your application uses offloaded sockets
+* You want to use the |SM| Host library
+* You're working with resource-constrained MCUs
+* You need to send both standard and proprietary AT commands
+
+Use the :ref:`sm_ppp_shell` when:
+
+* You want to use Zephyr's native networking stack
+* You prefer standard POSIX socket APIs
+* You need to test network performance
+* You're developing on Linux with the native simulator
+* You want seamless integration with Zephyr network services
+
+Both samples require the |SM| application to be running on an nRF91 Series device (nRF9160 or nRF9151).
+
+.. toctree::
+   :maxdepth: 2
+   :caption: Sample applications:
+
+   sm_at_client_shell
+   sm_ppp_shell

doc/samples/README.rst

@@ -1,4 +1,4 @@
-.. _sm_shell_sample:
+.. _sm_at_client_shell:
 
 |SM| AT Client Shell sample
 ###########################
@@ -72,7 +72,7 @@ The following table shows how to connect UART, DTR and RI pins of the DK to the
            - GPIO GND
 
       .. note::
-         You must disable the VCOM0 on the nRF54L15 DK to release the UART GPIO pins to use it with the :ref:`sm_shell_sample`.
+         You must disable the VCOM0 on the nRF54L15 DK to release the UART GPIO pins to use it with the :ref:`sm_at_client_shell`.
 
          * For nRF54L15 DK, you can use the `Board Configurator app`_ to disable the `Connect port VCOM0` setting.