Docs and README: Add STM32G474, B-G474E-DPOW1 board

Documentation/NuttX.html:
    Documentation/README.html:
    README.txt:
    boards/README.txt:

        Document initial support for the STM32G474 MCU and
        B-G474E-DPOW1 Discovery kit was added in NuttX-9.1.

Documentation/NuttX.html

@@ -1797,6 +1797,7 @@
       <li><a href="#stm32f433x">STMicro STM32 F433</a> <small>(STM32 F4 family, ARM Cortex-M4)</small></li>
       <li><a href="#stm32f446x">STMicro STM32 F446</a> <small>(STM32 F4 family, ARM Cortex-M4)</small></li>
       <li><a href="#stm32f46xxx">STMicro STM32 F46xx</a> <small>(STM32 F4 family, ARM Cortex-M4)</small></li>
+      <li><a href="#stm32g474x">STMicro STM32 G474x</a> <small>(STM32 G4 family, ARM Cortex-M4)</small></li>
       <li><a href="#stm32l4x2">STMicro STM32 L4x2</a> <small>(STM32 L4 family, ARM Cortex-M4)</small></li>
       <li><a href="#stm32l475">STMicro STM32 L475</a> <small>(STM32 L4 family, ARM Cortex-M4)</small></li>
       <li><a href="#stm32l476">STMicro STM32 L476</a> <small>(STM32 L4 family, ARM Cortex-M4)</small></li>
@@ -4846,6 +4847,35 @@ nsh>
   </td>
 </tr>
 
+<tr>
+  <td><br></td>
+  <td><hr></td>
+</tr>
+<tr>
+  <td><br></td>
+  <td>
+    <p>
+      <a name="stm32g474x"><b>STMicro STM32 G474</b>.</a>
+      One board is supported in this family:
+    </p>
+    <ul>
+      <li>
+        <p>
+          <b>B-G474E-DPOW1 Discovery Kit</b>.
+          Initial board support for the STMicro B-G474E-DPOW1 board from ST Micro was added in NuttX-9.1.  See the <a href="https://www.st.com/content/st_com/en/products/evaluation-tools/product-evaluation-tools/mcu-mpu-eval-tools/stm32-mcu-mpu-eval-tools/stm32-discovery-kits/b-g474e-dpow1.html" target="_blank">STMicro website</a> and the board <a href="https://github.com/apache/incubator-nuttx/blob/master/boards/arm/stm32/b-g474e-dpow1/README.txt" target="_blank">README</a> file for further information.
+        </p>
+      </li>
+    </ul>
+
+  <p><b>Status</b>:</p>
+  <ul>
+    <p>
+      <b>NuttX-9.1</b>.
+      Initial support for booting NuttX to a functional NSH prompt on this board.
+    </p>
+  </td>
+</tr>
+
 <tr>
   <td><br></td>
   <td><hr></td>

Documentation/README.html

@@ -232,6 +232,8 @@ nuttx/
  |   |   |- stm32/
  |   |   |   |- axoloti/
  |   |   |   |   `- <a href="https://bitbucket.org/nuttx/nuttx/src/master/boards/arm/stm32/axoloti/README.txt" target="_blank"><b><i>README.txt</i></b></a>
+ |   |   |   |- b-g474e-dpow1/
+ |   |   |   |   `- <a href="https://bitbucket.org/nuttx/nuttx/src/master/boards/arm/stm32/b-g474e-dpow1/README.txt" target="_blank"><b><i>README.txt</i></b></a>
  |   |   |   |- clicker2-stm32/
  |   |   |   |   `- <a href="https://bitbucket.org/nuttx/nuttx/src/master/boards/arm/stm32/clicker2-stm32/README.txt" target="_blank"><b><i>README.txt</i></b></a>
  |   |   |   |- cloudctrl/

README.txt

@@ -2112,6 +2112,8 @@ nuttx/
  |   |   |- stm32/
  |   |   |   |- axoloti/
  |   |   |   |   `- README.txt
+ |   |   |   |- b-g474e-dpow1/
+ |   |   |   |   `- README.txt
  |   |   |   |- clicker2-stm32/
  |   |   |   |   `- README.txt
  |   |   |   |- cloudctrl/

boards/README.txt

@@ -188,6 +188,10 @@ boards/arm/stm32/axoloti
   Support for the Axoloti synthesizer board based on the STMicro
   STM32F427IGH6 MCU.  See: http://www.axoloti.com/
 
+boards/arm/stm32/b-g474e-dpow1
+  Initial support for booting NuttX to a functional NSH prompt on the
+  STMicro B-G474E-DPOW1 Discovery kit with STM32G474RE MCU.
+
 boards/arm/stm32f0l0g0/b-l072z-lrwan1
   STMicro STM32L0 Discovery kit with LoRa/SigFox based on STM32L072CZ MCU.