documentation(boards): add documentation for native_sim (#172)

Signed-off-by: SorinO <sorin.olari2@gmail.com>

Author: SorinOlari

docs/boards/zephyr/native_sim.md

@@ -0,0 +1,158 @@
+# Zephyr Board: `native_sim`
+
+The **native_sim** board is a simulated Zephyr target that runs on your host Linux machine. It allows you to develop and test Zephyr applications without needing physical hardware. The native_sim board is particularly useful for rapid iteration, testing, and debugging.
+
+For detailed information, see the [Zephyr Native Simulator Documentation](https://docs.zephyrproject.org/latest/boards/native/native_sim/doc/index.html).
+
+## Architecture Support
+
+The **native_sim/native/64** (64-bit variant) is supported for the following Ocre samples:
+
+- **mini**
+- **demo**
+- **supervisor**
+
+**Note:** native_sim on 32-bit is not currently supported.
+
+## Networking
+
+For **supervisor** sample, native_sim board supports two distinct networking modes, configurable at build time:
+
+### 1. TAP Network Interface (Default)
+
+The TAP (TAP Virtual Network Interface) mode creates a virtual Ethernet network interface on your host machine, allowing the simulated board to communicate with the actual network.
+
+**Configuration:**
+
+- Uses `CONFIG_ETH_NATIVE_TAP=y` (enabled by default)
+- No additional configuration file needed
+
+### 2. NSOS (Native Sockets) Mode
+
+The NSOS (Native Sockets) mode uses the host machine's native socket implementation, allowing the simulated board to use the host's network stack directly.
+
+**Characteristics:**
+
+- Uses host native sockets API
+- Based on `CONFIG_NET_SOCKETS` and `CONFIG_NET_SOCKETS_OFFLOAD`
+- Uses separate `overlay-nsos.conf` configuration
+
+**Configuration File:**
+The NSOS mode uses board overlay configuration at:
+
+```
+boards/overlay-nsos.conf
+```
+
+## Build Instructions
+
+### Prerequisites
+
+Start with [Getting Started with Zephyr](../../GetStartedZephyr.md) to get a working build environment.
+
+### Building with TAP Networking (Default)
+
+To build native_sim with TAP networking:
+
+```bash
+west build -p always -b native_sim/native/64 src/samples/supervisor/zephyr/
+```
+
+### Building with NSOS Networking
+
+To build native_sim with Native Sockets (NSOS):
+
+```bash
+west build -p always -b native_sim/native/64 src/samples/supervisor/zephyr/ -- -DEXTRA_CONF_FILE=boards/overlay-nsos.conf
+```
+
+## Running the Simulation
+
+After building, regardless of which network method was used, run the native_sim application with the following command:
+
+```bash
+west build -t run
+```
+
+## Serial Console
+
+Unlike physical boards, native_sim outputs to your terminal directly. You will see output similar to:
+
+```
+*** Booting Zephyr OS build <version> ***
+
+ocre:~$
+```
+
+To interact with the Ocre shell, type commands directly in the same terminal.
+
+## Test Network Connectivity
+
+Once running, check network configuration with:
+
+```bash
+ocre:~$ net iface
+```
+
+**Example TAP mode output:**
+
+```bash
+Interface eth0 (0x4ba390) (Ethernet) [1]
+===================================
+Link addr : 02:00:5E:00:53:31
+MTU       : 1500
+Flags     : AUTO_START,IPv4,IPv6
+Device    : zeth0 (0x4b8b50)
+Status    : oper=UP, admin=UP, carrier=ON
+```
+
+**Example NSOS mode output:**
+
+```bash
+Interface net0 (0x4c1988) (<unknown type>) [1]
+=========================================
+MTU       : 1500
+Flags     : AUTO_START,IPv4,IPv6
+Device    : nsos_socket (0x4c0008)
+Status    : oper=UP, admin=UP, carrier=ON
+IPv4 unicast addresses (max 1):
+    192.0.2.1/255.255.255.0 overridable preferred infinite
+```
+
+## Memory Configuration
+
+The native_sim/native/64 variant includes enhanced memory configuration:
+
+```
+CONFIG_COMMON_LIBC_MALLOC_ARENA_SIZE=10485760  # 10 MB malloc arena
+```
+
+Flash and storage partitions are sized appropriately for simulation:
+
+```
+flash0:     32 MB (simulated)
+storage:    16 MB (for container images)
+```
+
+## Advantages for Development
+
+- **Fast iteration**: No hardware flashing required
+- **Easy debugging**: Direct terminal access and debugging tools
+- **Network simulation**: Test networking without physical network setup
+- **CI/CD compatible**: Can run in automated testing pipelines
+
+## Limitations
+
+- **64-bit only**: 32-bit native_sim is not supported
+- **Hardware peripherals**: No hardware-specific peripherals available (GPIO, sensors, etc.)
+
+## References
+
+- [Zephyr Native Simulator Documentation](https://docs.zephyrproject.org/latest/boards/native/native_sim/doc/index.html)
+- [Zephyr Networking Documentation](https://docs.zephyrproject.org/latest/connectivity/networking/index.html)
+- [Supervisor Sample Documentation](../../samples/supervisor.md)
+
+See the main documentation for:
+
+- [Zephyr Build System](../../BuildSystemZephyr.md)
+- [Get started Zephyr](../../GetStartedZephyr.md)