fixup! fixup! doc/guides: Add timer information to Porting Boards

Author: crasbe

doc/guides/advanced_tutorials/porting_boards.md

@@ -191,9 +191,51 @@ PORT_DARWIN ?= $(firstword $(sort $(wildcard /dev/tty.usbserial*)))
 PROGRAMMER ?= openocd
 ```
 
-### Timer Configurations
+### doc.md
+
+Although not explicitly needed, if upstreamed and as a general good
+practice, this file holds all `BOARD` documentation. This can include
+datasheet reference, documentation on how to flash, etc.
+
+The documentation must be under the proper doxygen group, you can compile the
+documentation by calling `make doc` and then open the generated html file on
+any browser.
+
+```markdown
+@defgroup    boards_foo FooBoard
+@ingroup     boards
+@brief       Support for the foo board
+@author      FooName BarName <[email protected]>
+
+#### User Interface
+
+  ...
+
+#### Using UART
+
+  ...
+
+#### Flashing the device
+
+  ...
+```
+
+Previously documentation was contained in `doc.txt` files with C-style comment
+blocks. This style has been deprecated in favor of using `doc.md` files in
+Markdown format, which eliminates formatting and interpretation issues.
+Old style files will continually be replaced by the new format.
+
+Up to version `0.9.2` the [riotgen](https://pypi.org/project/riotgen/) tool
+will generate `doc.txt` files instead of `doc.md` files. You can upgrade it to
+the latest version with
+
+```bash
+pip install --upgrade riotgen
+```
+
+## Timer Configuration
 
-#### Timer Width
+### Timer Width
 
 Some resource constrained or low-power microcontrollers only have 16-bit
 wide timer registers available. By default `ztimer` assumes a timer width of
@@ -221,7 +263,7 @@ For example: If you observe "erratic" blinking patterns in
 `examples/basic/blinky`, make sure to check if the sizes match.
 :::
 
-#### Overhead Calibration
+### Overhead Calibration
 
 When using the high level timer `ztimer` there is an overhead in calling the
 [ztimer_sleep](https://doc.riot-os.org/group__sys__ztimer.html#gade98636e198f2d571c8acd861d29d360)
@@ -266,48 +308,6 @@ Alternatively, the pseudomodule
 can be used in an application to enable automatic timer offset compensation at board startup.
 This however incurs overhead both in the text segment and at bootup time.
 
-### doc.md
-
-Although not explicitly needed, if upstreamed and as a general good
-practice, this file holds all `BOARD` documentation. This can include
-datasheet reference, documentation on how to flash, etc.
-
-The documentation must be under the proper doxygen group, you can compile the
-documentation by calling `make doc` and then open the generated html file on
-any browser.
-
-```markdown
-@defgroup    boards_foo FooBoard
-@ingroup     boards
-@brief       Support for the foo board
-@author      FooName BarName <[email protected]>
-
-#### User Interface
-
-  ...
-
-#### Using UART
-
-  ...
-
-#### Flashing the device
-
-  ...
-```
-
-Previously documentation was contained in `doc.txt` files with C-style comment
-blocks. This style has been deprecated in favor of using `doc.md` files in
-Markdown format, which eliminates formatting and interpretation issues.
-Old style files will continually be replaced by the new format.
-
-Up to version `0.9.2` the [riotgen](https://pypi.org/project/riotgen/) tool
-will generate `doc.txt` files instead of `doc.md` files. You can upgrade it to
-the latest version with
-
-```bash
-pip install --upgrade riotgen
-```
-
 ## Helper Tools
 
 To help you start porting a board, the RIOT build system provides the