doc: devicetree: change doxygen groups

Create a top level devicetree group, and put everything underneath it.

Signed-off-by: Martí Bolívar <marti.bolivar@nordicsemi.no>

include/devicetree.h

@@ -24,6 +24,9 @@
 
 /**
  * @brief devicetree.h API
+ * @defgroup devicetree Devicetree
+ * @{
+ * @}
  */
 
 /*
@@ -51,6 +54,7 @@
 
 /**
  * @defgroup devicetree-generic-id Node identifiers
+ * @ingroup devicetree
  * @{
  */
 
@@ -240,6 +244,7 @@
 
 /**
  * @defgroup devicetree-generic-prop Property accessors
+ * @ingroup devicetree
  * @{
  */
 
@@ -818,6 +823,7 @@
 
 /**
  * @defgroup devicetree-generic-chosen Chosen nodes
+ * @ingroup devicetree
  * @{
  */
 
@@ -836,6 +842,7 @@
 
 /**
  * @defgroup devicetree-generic-exist Existence checks
+ * @ingroup devicetree
  * @{
  */
 
@@ -997,6 +1004,7 @@
 
 /**
  * @defgroup devicetree-generic-bus Bus helpers
+ * @ingroup devicetree
  * @{
  */
 
@@ -1093,6 +1101,7 @@
 
 /**
  * @defgroup devicetree-inst Instance-based devicetree APIs
+ * @ingroup devicetree
  * @{
  */
 

include/devicetree/adc.h

@@ -18,6 +18,7 @@ extern "C" {
 
 /**
  * @defgroup devicetree-adc Devicetree ADC API
+ * @ingroup devicetree
  * @{
  */
 

include/devicetree/clocks.h

@@ -18,6 +18,7 @@ extern "C" {
 
 /**
  * @defgroup devicetree-clocks Devicetree Clocks API
+ * @ingroup devicetree
  * @{
  */
 

include/devicetree/dma.h

@@ -18,6 +18,7 @@ extern "C" {
 
 /**
  * @defgroup devicetree-dmas Devicetree dma API
+ * @ingroup devicetree
  * @{
  */
 

include/devicetree/gpio.h

@@ -19,6 +19,7 @@ extern "C" {
 
 /**
  * @defgroup devicetree-gpio Devicetree GPIO API
+ * @ingroup devicetree
  * @{
  */
 

include/devicetree/spi.h

@@ -18,6 +18,7 @@ extern "C" {
 
 /**
  * @defgroup devicetree-spi Devicetree SPI API
+ * @ingroup devicetree
  * @{
  */
 

include/devicetree/zephyr.h

@@ -14,6 +14,7 @@
 
 /**
  * @defgroup devicetree-zephyr Zephyr's /chosen nodes
+ * @ingroup devicetree
  * @{
  */