Fix back-to-front description of IRQ priority in doxygen (raspberrypi…

…#245)

src/rp2_common/hardware_irq/include/hardware/irq.h

@@ -123,9 +123,12 @@ typedef void (*irq_handler_t)(void);
  *  \ingroup hardware_irq
  *
  * \param num Interrupt number
- * \param hardware_priority Priority to set. Hardware priorities range from 0 (lowest) to 255 (highest) though only
- * the top 2 bits are significant on ARM Cortex M0+. To make it easier to specify higher or lower priorities
- * than the default, all IRQ priorities are initialized to PICO_DEFAULT_IRQ_PRIORITY by the SDK runtime at startup.
+ * \param hardware_priority Priority to set.
+ * Numerically-lower values indicate a higher priority. Hardware priorities
+ * range from 0 (highest priority) to 255 (lowest priority) though only the
+ * top 2 bits are significant on ARM Cortex-M0+. To make it easier to specify
+ * higher or lower priorities than the default, all IRQ priorities are
+ * initialized to PICO_DEFAULT_IRQ_PRIORITY by the SDK runtime at startup.
  * PICO_DEFAULT_IRQ_PRIORITY defaults to 0x80
  */
 void irq_set_priority(uint num, uint8_t hardware_priority);