bluetooth: rpc: add nrf53 cpunet enable code

Added the code for enabling nRF53 network core in the Bluetooth
RPC configuration. The change is required as the newly introduced
Kconfig - CONFIG_SOC_NRF53_CPUNET_ENABLE - for enabling the network
core at the SoC level cannot be enabled in projects that use the
CONFIG_BT Kconfig.

Ref: NCSDK-29186

Signed-off-by: Kamil Piszczek <Kamil.Piszczek@nordicsemi.no>

subsys/bluetooth/rpc/CMakeLists.txt

@@ -11,3 +11,4 @@ target_include_directories(subsys_bluetooth_rpc INTERFACE ${CMAKE_CURRENT_SOURCE
 add_subdirectory(common)
 add_subdirectory_ifdef(CONFIG_BT_RPC_CLIENT client)
 add_subdirectory_ifdef(CONFIG_BT_RPC_HOST host)
+add_subdirectory(soc)

subsys/bluetooth/rpc/soc/CMakeLists.txt

@@ -0,0 +1,7 @@
+#
+# Copyright (c) 2024 Nordic Semiconductor
+#
+# SPDX-License-Identifier: LicenseRef-Nordic-5-Clause
+#
+
+zephyr_library_sources_ifdef(CONFIG_SOC_NRF5340_CPUAPP nrf53_cpunet_enable.c)

subsys/bluetooth/rpc/soc/nrf53_cpunet_enable.c

@@ -0,0 +1,37 @@
+/*
+ * Copyright (c) 2024 Nordic Semiconductor ASA
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#include <nrf53_cpunet_mgmt.h>
+
+#include <zephyr/kernel.h>
+#include <zephyr/init.h>
+
+#include <hal/nrf_spu.h>
+
+static int nrf53_cpunet_init(void)
+{
+#if !defined(CONFIG_TRUSTED_EXECUTION_NONSECURE)
+	/* Retain nRF5340 Network MCU in Secure domain (bus
+	 * accesses by Network MCU will have Secure attribute set).
+	 */
+	nrf_spu_extdomain_set((NRF_SPU_Type *)DT_REG_ADDR(DT_NODELABEL(spu)), 0, true, false);
+#endif /* !defined(CONFIG_TRUSTED_EXECUTION_NONSECURE) */
+
+#if !defined(CONFIG_TRUSTED_EXECUTION_SECURE)
+	/*
+	 * Building Zephyr with CONFIG_TRUSTED_EXECUTION_SECURE=y implies
+	 * building also a Non-Secure image. The Non-Secure image will, in
+	 * this case do the remainder of actions to properly configure and
+	 * boot the Network MCU.
+	 */
+
+	nrf53_cpunet_enable(true);
+#endif /* !CONFIG_TRUSTED_EXECUTION_SECURE */
+
+	return 0;
+}
+
+SYS_INIT(nrf53_cpunet_init, POST_KERNEL, CONFIG_KERNEL_INIT_PRIORITY_DEVICE);