arch/xtensa/src/common: Create SoC-specific initialization routine

This commits adds a function that can be implemented by any vendor
to allow SoC-specific functions to be called by `up_initialize`.
Please note that `up_initialize` is provided by the arch level, but
it doesn't allow SoC-specific initialization. Although it could be
possible to run such initialization on board-level, semantically
it isn't related to the board, but with the SoC. As an example of
such implementation, some SoCs require RTC subsystem initialization
to occur before the OS is completely initialized.

Signed-off-by: Tiago Medicci Serrano <tiago.medicci@espressif.com>

arch/xtensa/src/common/xtensa.h

@@ -266,6 +266,10 @@ void xtensa_clrpend_irq(int irq);
 void weak_function xtensa_dma_initialize(void);
 #endif
 
+/* SoC-specific CPU initialization */
+
+void weak_function xtensa_soc_initialize(void);
+
 /* Memory management */
 
 #if CONFIG_MM_REGIONS > 1

arch/xtensa/src/common/xtensa_initialize.c

@@ -106,5 +106,12 @@ void up_initialize(void)
 
   xtensa_usbinitialize();
 
+#ifdef CONFIG_HAVE_WEAKFUNCTIONS
+  if (xtensa_soc_initialize)
+#endif
+    {
+      xtensa_soc_initialize();
+    }
+
   board_autoled_on(LED_IRQSENABLED);
 }