doc: random number generation

Add random number generation APIs to the HTML documentation.
Fix style issues.

Signed-off-by: Heinrich Schuchardt <[e-mail]>

MAINTAINERS

···
 R:	Heinrich Schuchardt <[e-mail]>
 S:	Maintained
 F:	cmd/rng.c
+F:	doc/api/rng.rst
 F:	drivers/rng/
 F:	drivers/virtio/virtio_rng.c
 F:	include/rng.h

doc/api/index.rst

···
    dfu
    efi
    linker_lists
+   rng
    serial
    unicode

doc/api/rng.rst

···
+.. SPDX-License-Identifier: GPL-2.0+
+.. Copyright (c) 2018 Heinrich Schuchardt
+
+Random number generation
+========================
+
+Hardware random number generation
+---------------------------------
+
+.. kernel-doc:: include/rng.h
+   :internal:
+
+Pseudo random number generation
+-------------------------------
+
+.. kernel-doc:: include/rand.h
+   :internal:

include/rand.h

···
 /**
  * rand() - Get a 32-bit pseudo-random number
  *
- * @returns next random number in the sequence
+ * Return:	next random number in the sequence
  */
 unsigned int rand(void);
 
···
  * This version of the function allows multiple sequences to be used at the
  * same time, since it requires the caller to store the seed value.
  *
- * @seed value to use, updated on exit
- * @returns next random number in the sequence
+ * @seedp:	seed value to use, updated on exit
+ * Return:	 next random number in the sequence
  */
 unsigned int rand_r(unsigned int *seedp);
 

include/rng.h

···
 
 /**
  * dm_rng_read() - read a random number seed from the rng device
+ *
+ * The function blocks until the requested number of bytes is read.
+ *
+ * @dev:	random number generator device
  * @buffer:	input buffer to put the read random seed into
- * @size:	number of bytes of random seed read
- *
- * Return: 0 if OK, -ve on error
+ * @size:	number of random bytes to read
+ * Return:	0 if OK, -ve on error
  */
 int dm_rng_read(struct udevice *dev, void *buffer, size_t size);
 
-/* struct dm_rng_ops - Operations for the hwrng uclass */
+/**
+ * struct dm_rng_ops - operations for the hwrng uclass
+ *
+ * This structures contains the function implemented by a hardware random
+ * number generation device.
+ */
 struct dm_rng_ops {
 	/**
-	 * @read() - read a random number seed
+	 * @read:	read a random bytes
 	 *
-	 * @data:	input buffer to read the random seed
-	 * @max:	total number of bytes to read
+	 * The function blocks until the requested number of bytes is read.
 	 *
-	 * Return: 0 if OK, -ve on error
+	 * @read.dev:		random number generator device
+	 * @read.data:		input buffer to read the random seed into
+	 * @read.max:		number of random bytes to read
+	 * @read.Return:	0 if OK, -ve on error
 	 */
 	int (*read)(struct udevice *dev, void *data, size_t max);
 };