xen: sysctl: Add doxygen comments for sysctl functions

Document all of the public functions in the sysctl API with doxygen

Signed-off-by: Mykyta Poturai <[email protected]>
Acked-by: Dmytro Firsov <[email protected]>

include/zephyr/xen/dom0/sysctl.h

@@ -3,13 +3,37 @@
  *
  * SPDX-License-Identifier: Apache-2.0
  */
+
+/**
+ * @file
+ *
+ * @brief Xen System Control Interface
+ */
+
 #ifndef __XEN_DOM0_SYSCTL_H__
 #define __XEN_DOM0_SYSCTL_H__
 #include <zephyr/xen/generic.h>
 #include <zephyr/xen/public/sysctl.h>
 #include <zephyr/xen/public/xen.h>
 
+/**
+ * @brief Retrieves information about the host system.
+ *
+ * @param[out] info A pointer to a `struct xen_sysctl_physinfo` structure where the
+ *             retrieved information will be stored.
+ * @return 0 on success, or a negative error code on failure.
+ */
 int xen_sysctl_physinfo(struct xen_sysctl_physinfo *info);
+
+/**
+ * @brief Retrieves information about Xen domains.
+ *
+ * @param[out] domaininfo A pointer to the `xen_domctl_getdomaininfo` structure
+ *                        to store the retrieved domain information.
+ * @param first The first domain ID to retrieve information for.
+ * @param num The maximum number of domains to retrieve information for.
+ * @return 0 on success, or a negative error code on failure.
+ */
 int xen_sysctl_getdomaininfo(struct xen_domctl_getdomaininfo *domaininfo,
 			     uint16_t first, uint16_t num);