Add Multicore SMP on Armv8-M ports

.github/.cSpellWords.txt

@@ -433,6 +433,7 @@ LDRAS
 ldrb
 ldrbs
 LDRBS
+ldrex
 LDRNE
 ldsr
 ldxr

.github/scripts/kernel_checker.py

@@ -2,6 +2,7 @@
 #/*
 # * FreeRTOS Kernel <DEVELOPMENT BRANCH>
 # * Copyright (C) 2024 Amazon.com, Inc. or its affiliates. All Rights Reserved.
+# * Copyright 2026 Arm Limited and/or its affiliates <open-source-office@arm.com>
 # *
 # * SPDX-License-Identifier: MIT
 # *
@@ -157,9 +158,10 @@
 
 
 FREERTOS_COPYRIGHT_REGEX = r"^(;|#)?( *(\/\*|\*|#|\/\/))? Copyright \(C\) 20\d\d Amazon.com, Inc. or its affiliates. All Rights Reserved\.( \*\/)?$"
+ARM_COLLAB_YEAR_REGEX = r"20\d\d(?:-20\d\d|, 20\d\d)?"
 
 FREERTOS_ARM_COLLAB_COPYRIGHT_REGEX = r"(^(;|#)?( *(\/\*|\*|#|\/\/))? Copyright \(C\) 20\d\d Amazon.com, Inc. or its affiliates. All Rights Reserved\.( \*\/)?$)|" + \
-                                      r"(^(;|#)?( *(\/\*|\*|#|\/\/))? Copyright 20\d\d(-20\d\d)? Arm Limited and/or its affiliates( +<open-source-office@arm\.com>)?( \*\/)?$)|" + \
+                                      rf"(^(;|#)?( *(\/\*|\*|#|\/\/))? Copyright { ARM_COLLAB_YEAR_REGEX } Arm Limited and/or its affiliates( +<open-source-office@arm\.com>)?( \*\/)?$)|" + \
                                       r"(^(;|#)?( *(\/\*|\*|#|\/\/))? Copyright \(c\) 20\d\d(-20\d\d)? Arm Technology \(China\) Co., Ltd.All Rights Reserved\.( \*\/)?$)|" + \
                                       r"(^(;|#)?( *(\/\*|\*|#|\/\/))? <open-source-office@arm\.com>( \*\/)?$)"
 

portable/ARMv8M/non_secure/ReadMe.txt

@@ -1,6 +1,6 @@
 This directory tree contains the master copy of the FreeRTOS Armv8-M and
 Armv8.1-M ports.
-Do not use the files located here!  These file are copied into separate
+Do not use the files located here!  These files are copied into separate
 FreeRTOS/Source/portable/[compiler]/ARM_[CM23|CM33|CM52|CM55|CM85|STAR_MC3]_NNN directories
 prior to each FreeRTOS release.
 
@@ -9,3 +9,54 @@ FreeRTOS/Source/portable/[compiler]/ARM_[CM23|CM33|CM52|CM55|CM85|STAR_MC3] dire
 
 If your Armv8-M/Armv8.1-M application does not use TrustZone then use the files from
 the FreeRTOS/Source/portable/[compiler]/ARM_[CM23|CM33|CM52|CM55|CM85|STAR_MC3]_NTZ directories.
+
+Note:
+The Armv8-M ports support SMP (multicore) systems when both MPU and TrustZone are disabled.
+However, this has only been validated on Arm Cortex-M33 Non-TrustZone Non-MPU port.
+
+SMP Boot Sequence
+---------------------------------------
+
+Primary core flow:
+
+1. Perform core-specific and shared initialization (e.g., zero-initialize `.bss`).
+2. Jump to `main()`, create user tasks, optionally pin tasks to specific cores.
+3. Call `vTaskStartScheduler()` which invokes `xPortStartScheduler()`.
+4. `xPortStartScheduler()` configures the primary core tick timer and signals secondary cores that shared init is complete using the `ucPrimaryCoreInitDoneFlag` variable.
+5. Call the application-defined `configWAKE_SECONDARY_CORES` function.
+6. Wait until all secondary cores report as brought up.
+7. Once all cores are up, call `vStartFirstTask()` to schedule the first task on the primary core.
+
+Secondary core flow:
+
+1. Perform core-specific initialization.
+2. Wait until the primary core signals that shared initialization has completed (that is, `ucPrimaryCoreInitDoneFlag` is set to 1). Once this occurs,
+the application-defined `configWAKE_SECONDARY_CORES` function is invoked by the primary core to carry out the subsequent steps.
+3. Program the inter-processor signaling mechanism (e.g., Arm Doorbell Mechanism) to be used by the kernel to interrupt that core and request that it perform a context switch.
+4. Call `vPortConfigureInterruptPriorities` function to setup per core interrupt priorities.
+5. If Pointer Authentication (PAC) or Branch Target Identification (BTI) is supported, call `vConfigurePACBTI` with `pdTRUE` as the input parameter to configure the per-core special-purpose CONTROL register
+with the appropriate PACBTI settings.
+6. Signal the primary that this secondary is online and ready by setting its flag in the `ucSecondaryCoresReadyFlags` array.
+7. Issue an SVC with immediate value `102` (portSVC_START_SCHEDULER), which will call `vRestoreContextOfFirstTask()` to start scheduling on this core.
+
+
+Inter-core notification
+---------------------------------------
+
+On SMP systems the application must provide an implementation of the `vInterruptCore( uint8_t ucCoreID )` function. The kernel calls this function
+to interrupt another core and request that it perform a context switch (e.g., when a higher-priority task becomes ready on that core).
+
+Typical platform implementation: write a doorbell flag/bit or other inter-processor signaling register targeting `ucCoreID`. This should cause a
+"doorbell" (or equivalent) IRQ on the secondary core. In the secondary core’s doorbell IRQ handler, check the reason for the interrupt and, if it is a
+schedule request, trigger a context switch (i.e., by calling `portYIELD_FROM_ISR`).
+
+Notes:
+
+* `vInterruptCore` is declared weak in the port so that platforms can override it. If your hardware lacks a dedicated doorbell, use any available
+inter-core interrupt/messaging mechanism to achieve the same effect.
+
+* The application must define `configCORE_ID_REGISTER`, usually in `FreeRTOSConfig.h` to the memory-mapped address of the platform register used
+to read the current core ID. The port reads this register to determine the executing core and to index per-core scheduler state.
+
+* The application must define `configWAKE_SECONDARY_CORES`, usually in `FreeRTOSConfig.h`, to point to the application/platform-specific function
+that wakes up and make the secondary cores ready after the primary core completes initialisation.