Add full automotive RTOS project

Add kernel (Cortex-M0/M3/M4, Tricore, S32K, RISC-V ports), drivers,
middleware (CAN stack, diagnostics, safety), applications, board
support, build/test tooling, and documentation.

kernel/include/semaphore.h

@@ -0,0 +1,37 @@
+/**
+ * @file semaphore.h
+ * @brief Semaphore synchronization primitive
+ */
+
+#ifndef SEMAPHORE_H
+#define SEMAPHORE_H
+
+#include "kernel.h"
+
+/* Semaphore Types */
+typedef enum {
+    SEMAPHORE_BINARY = 0,
+    SEMAPHORE_COUNTING = 1,
+    SEMAPHORE_MUTEX = 2
+} SemaphoreType_t;
+
+/* Semaphore Control Block */
+typedef struct {
+    SemaphoreType_t type;
+    uint32_t count;
+    uint32_t max_count;
+    TaskHandle_t owner;  /* For mutex */
+    uint8_t priority_ceiling;
+    TaskHandle_t* waiting_tasks;
+    uint32_t waiting_count;
+} Semaphore_t;
+
+/* Semaphore Functions */
+KernelStatus_t semaphore_create(Semaphore_t* sem, SemaphoreType_t type,
+                                uint32_t initial_count, uint32_t max_count);
+KernelStatus_t semaphore_take(Semaphore_t* sem, TimeOut_t timeout);
+KernelStatus_t semaphore_give(Semaphore_t* sem);
+KernelStatus_t semaphore_delete(Semaphore_t* sem);
+uint32_t semaphore_get_count(Semaphore_t* sem);
+
+#endif /* SEMAPHORE_H */