Mostly costmetic updates

git-svn-id: http://svn.code.sf.net/p/nuttx/code/trunk@5452 42af7a65-404d-4744-a932-0658087f49c3

nuttx/arch/z16/src/common/up_doirq.c

@@ -90,6 +90,15 @@ FAR chipreg_t *up_doirq(int irq, FAR chipreg_t *regs)
     {
       FAR chipreg_t *savestate;
 
+      /* Nested interrupts are not supported in this implementation.  If
+       * you want to implement nested interrupts, you would have to (1) change
+       * the way that current_regs is handled and (2) the design associated
+       * with CONFIG_ARCH_INTERRUPTSTACK.  The savestate variable will not
+       * work for that purpose as implemented here because only the outermost
+       * nested interrupt can result in a context switch (it can probably be
+       * deleted).
+       */
+
       /* Current regs non-zero indicates that we are processing
        * an interrupt; current_regs is also used to manage
        * interrupt level context switches.